1998 Deville Has Goten Loud

[GreenMachine]

Rather than hijacking all the Muffler threads I thought I should start my own. The FSM doesn't really give much in the way of specs for the system (still haven't figured out where these things list part numbers) but from what I gather it goes something like this:

__________________________________________Muffler

crossover--pipe--catalytic converter--pipe-----Y-Pipe=

__________________________________________Muffler

Out of those pieces it seems like the only pieces "muffling" the sound are Cat and Mufflers (my FSM makes no mention of a Resonator). My concern is that with my misfire problems I killed the Cat. Both mufflers when I have my ear near them are making the same sound, and I was thinking that both mufflers going at the same time is kinda rare. Could misfires damage the mufflers instead of the cat? Worst case is it killed cat and both mufflers, there were some pretty bad sounds when I was on the highway diagnosing the car. At one point climbing a hill it felt like a hammer was hitting the floor boards. Glad all that's fixed.....now the car is just getting louder and louder, but still smooth in operation. Slowly but surely its becoming a hot rod sound, then it will bleed me ear when what ever is dieing dies.

So if it is the cat what do you recommend as replacement? If its the mufflers I'm pretty set on some of the Borlas, seem to be priced pretty good, people who have them like the sound and get good comments, what size would I need? I think I recall people saying the pipes were 2 inch so 2inch mufflers would be "bolt on" right, or do I need to go slightly bigger with 2.25 inch? The reason I'm considering aftermarket is the OEMs seem about the same price as the Borla options.

The thing that concerns me is that most of the threads I've read have been post 2000 Devilles and post 98 Sevilles. I don't have the "quad" look to my pipes with the nice chrome tips, just some down tips that don't have anything fancy and are pretty hidden.

The car will be going in for paint in the next couple weeks and I think I'll just have my long time trusted shop take a look at it, rotate the tires, lube it up, change the oil and such since its getting cold and the rain doesn't want to stop for long enough for me to do any work myself.

http://www.borla.com/products/product_mult...|Turbo+Mufflers

[Ranger]

Could misfires damage the mufflers instead of the cat?

No. I am not even sure if a misfire would kill a Cat, but I know it will not harm the muffler. If it is getting loud, I would suspect the mufflers.

[KHE]

I'd suspect the muffler(s) - jack up the car and start it up and go over the whole system and you should find the leak.

I would contact Brasington's - gmotors.com for the factory exhaust parts - going with a louder exhaust may seem appealing but you may quickly grow tired of the louder exhaust.

[Cadillac Jim]

If the cat goes, it will clog, and make the car quieter if anything. Even if the cat does something that opens it up, it won't make the car louder, I don't think. And, yes, both mufflers will go at about the same time, particularly if they are brought down by an engine problem. On the other hand, your symptoms sound more like an exhaust leak at one of the cat clamps, probably the rear one, so you might look at the whole system from a simple repair standpoint before you begin. You won't hear anything from under the console when the mufflers go, even if they fall off in the street. Under the console is the back of the cat where the clamp to the long pipe is.

My experience with my Pontiac Grand Am with its Quad 4 HO was that, when a catalytic converter's ceramic element cracks, the torque curve moves down the RPM scale and fuel economy begins to decrease, particularly highway mileage. You can hear a rattle from under the car at idle that gets gradually worse. As the ceramic breaks up, the rattling gets louder, then changes gradually to a cement-mixer sound, the torque curve moves right through zero and the fuel economy drops even around town, and the high end horsepower goes away. My Pontiac was out of warranty by then and my dealer told me to go to Midas or other good muffler shop because OEM catalytic converters from GM are very expensive and there is no reason not to go to Midas or Meneke or Brake-O, or other reputable muffler shop.

I talked to Meineke about my system before they got the car. And, I looked under it with the body shop when they were taking it apart and deciding to take it to Meineke. The system is high-grade galvanized steel throughout, not stainless steel. Due to the fact that the torque curve seemed to be moving down the RPM scale, I thought that the cat was going bad. Also, it seemed to me that the maximum peak highway mileage wasn't what it should be. Meineke told me these things:

• 120,000 miles won't bring down a catalytic converter.
• Usually when a catalytic converter goes bad, it's because of engine problems. Coolant through the exhaust system will eventually bring down a catalytic converter.
• Oil burning won't bring down a catalytic converter, within reason. Vast amounts of oil might overheat one.
• An OEM catalytic converter is very expensive. They carry one that they can use to replace mine just fine for under $300. There is no quality difference.
• My car doesn't need a low-restriction catalytic converter.

When Meineke got my car, they looked at my cat and said it was OK. We left it alone. When I got the car back with the Borlas, the torque curve was fine and the highway maximum peak gas mileage was fine. In fact, I am getting 1-2 mpg better overall fuel economy. So, the cat is fine. The mufflers were going bad, probably because of the coolant that the old engine was beginning to put through them.

The Borlas I have are from the XS Pro line:

http://www.borla.com/proxs/pages/muflroff_ctr.php

This is their performance line. The mufflers are slightly wider than the general replacement turbos at 14" X 4" X x 19 1/2" (the turbos are 13 1/4" X 4" X 19 1/2"), apparently to provide the same silencing with less restriction. I quite thoroughly recommend them. The Northstar system is inherently quiet, and the exhaust note with the Borla Pro XS is quite acceptable. Riding with the windows closed allows normal use of the radio and conversation at any speed. I recently gave a priest a ride on a 30-mile road trip, each way, and he never said a word. My wife likes my Borla Pro XS exhaust note. I like the gas mileage and performance. And, yes, I like the V8 sound.

I have a new engine, and it has only about 3,500 miles on it, so maybe that needs to be taken into consideration. I will say that, once I got my Michelin Pilot Sport A/S tires about a year ago, I could nail it from a standing start on a really good surface without spinning the tires, and that was true up until the Borlas went on. No more. I must be careful on most surfaces all through low gear. The top end is noticeably better, too.

The worst thing I can say about the exhaust note is that adjacent cars and trucks riding with the windows open now know how effortlessly my ETC handles just about everything, and it's quite intimidating to the lead-foot sport-utes to see me more than matching traffic at very light throttle and shifting leisurely at low RPM, and quite often coming off the throttle completely. When my lead foot manifests itself, it's never anywhere near another car; the WOT exhaust note is the typical turbo muffler stern growl through mid-range, with a hint of a Ferrari hoot as the RPM goes above 4,000 through the 6,200 RPM red-line, which it does effortlessly, as you know. That sound can be stunning to those who think of a Cadillac as a boat.

Above 5,500 RPM, I can hear a hint of a cat hiss through the exhaust note, indicating to me that I could get a little more torque up there with a low-restriction catalytic converter; I have no plans to do that. What I would get wouldn't be worth the $$$ and the risk of modifying my exhaust system. The effects on the torque curve of any change in the exhaust system increase as you get closer to the engine, and it seems clear to me from the header design that there are at least two high RPM resonances that in the system that are bounded by the catalytic converter, and I'm content to leave that alone. You may want that horsepower at the very top of the RPM curve and you can bet that it will improve acceleration times. I may change my mind if I hear from others here that it works well for them.

[GreenMachine]

Tanks for the replies.

I'll have to see what I have as options, not sure what shipping would cost for Borlas and I haven't seen any shops around here sporting their name.

When I look up the part numbers for the left and right mufflers one is a fare bit more expensive than the other? I'll have to get under their to take a look but is one of the mufflers "part" of the y pipe and then the second one hooks on to that (in other words the system is basically a modifed version of the prevous single muffler system?).

The main question I need answered is what size the 98 Devilles take, 2 inch, or 2.25. or is that all up to the muffler shop to make fit?

[KHE]

One of the mufflers has a "Y-pipe" - it's normal. If you order factory parts, they will bolt right up.

[epricedright]

Green, are you sure you want the sound of Borlas? Doesn't quite fit a Deville does it?

But hey, if that's what you like, go for it!

[nigel]

i'm not sure why but the stock answer in the US regarding a cat is that it is only shot if it has clogged up.

this really isn't completely true. modern cats have the catalytic material bonded to a ceramic honeycomb. if you ground the cat or even overheat it the ceramic honeycomb can break. once it's broken the pieces can block the rest of the cat or they can be blown out of the tailpipe in small pieces.

i have personal experience of 2 cats that completely lost their insides, all that was left was an empty case.

a misfire can damage a cat, the unburnt fuel hits the cat, which is very hot, and detonates. this can break the material by overheating it.

modern cats are very often overlooked by mechanics because modern engine management systems regulate the exhaust gasses to keep the cat from getting too hot (egr and AIR systems can help cool a cat)

a car with a high tailpipe emission reading often has the cat completely overlooked, the electronic parts are blamed in error.

[Cadillac Jim]

Cadillacs and probably all reasonably late model GM cars have an extra oxygen sensor on the output side of the catalytic converter. If the catalytic converter quits converting for any reason, you will get a P0420 code and the Check Engine light will come on.

If you use Borlas, they will cut the pipe just in front of the existing mufflers and you will use the existing rear Y and the bend that follows it from each side. You use the same Borla muffler for each side. The general replacement turbo is Borla part number 40652, and the Pro XS part number is 40357. I recommend the 40357. These are 2 ¼" in and out. The pipes from the rear Y are 2" but 2 1/4" mufflers easy to work with and they have a bigger hole through the muffler. The pipes coming back from the rear Y are hooked to the two Borlas on the offset side, and the offset is used to keep the mufflers apart. An extension is fabricated to make up the difference in length of the Borlas and the stock mufflers and hooks the Borlas to the stock tips. The pipes and tips from the stock mufflers are then welded on to the extension, and you are set. Precise fit of this welded setup is something you want a good muffler shop to work out.

The stock tips include a heavy-duty inverse Y for each tip that probably helps keep the exhaust note from including any harshness by reflecting high-pitched sound back into the muffler. The tips are double, and thus are air cooled, and this protects your bumper cover from excess heat. If you decide to go with aftermarket tips, be sure and use the double ones. I couldn't find any that looked right on my ETC so I ended up using tips from a 1994 STS. I recommend the stock tips.

I recommend the Pro XS series. They are specifically designed for performance and I don't think that they are any louder than the general replacement turbos. The cost is about the same, about $105 each; you might do better if you shop around online. This guy offers the 40357 for $75:

http://www.wickednicky.com/borla_pro_xs.html

This guy offers the 40652 for $105:

http://store.summitracing.com/egnsearch.asp?N=400310

You are well-advised to get them online rather than shop around for local dealers, unless you get real lucky or are willing to drive. Borla has scads of national dealers that sell online or on the phone on their web site, or you can just Google one of the part numbers. Jus show up at the Meineke with the Borlas in the trunk. They can handle the rest.

If you don't like the sound, have the muffler shop take out the Borlas and put your old stock mufflers back in. I predict that you will drive out, notice the performance improvement instantly, notice the gas mileage increase over the next few days, get an approving comment from your wife on the exhaust note, and never look back.

If you decide to go with the stock mufflers, the Y comes with one of them and both of them come with tips. They are clamped onto the pipes that come out of the Y. That way, even a dealer can get them everything lined up properly -- a fabrication setup isn't needed. You could probably do it yourself. The stock mufflers will cost more than the Borlas, shipping, and installation combined.

[GreenMachine]

Thanks for the info. Borla shows Turbo for sized upto small block V8's, those XS might be more than I need, any differance in sound that you know of? I'm not really keen on what the differances are, one more free flowing? At 75 I almost couldn't resist grabing those.

Also I may have not made it clear, but my car doesn't seem to have tips of any kind, just some nearly hidden tips. I'lll take a picture but there really isn't room for dual tips back there (the bumper is cut for single tailpipe/tip)

[attachmentid=2873]

This is the closest to what I think the system looks like, minus the dual tips, I'll have to crawl under their and take a look but this looks just like the picture in my FSM (FSM conveintly cuts off all the pictures before it shows the tips).

[attachmentid=2874]

*pictures are from google image search

This is good for a laugh:

http://cgi.ebay.com/ebaymotors/Exhaust-Tip...VQQcmdZViewItem

Green, are you sure you want the sound of Borlas? Doesn't quite fit a Deville does it?

But hey, if that's what you like, go for it!

From all that I have read, and I've read alot, sometimes twice now, these Borlas are quite cruising, but when you WANT to hear it, you hear it, and thats exactly what I'm looking for, a deville that around town, with minmal throttle, you know just crusing the 30mph zones where you don't need to go over 2000rpm, it will be like "normal" with better fuel economy, on the highway, crusing, nothing too noticeable until you step on it or partly and hear that nice low grunt while the car remains in overdrive and you accidently end up at 90

[Cadillac Jim]

Borla has three lines of mufflers for general-purpose street cars. The general replacement turbo mufflers come in two sizes, small block (Turbo) and large block (Turbo XL). Then there's the Pro XS series:

http://www.borla.com/proxs/pages/mufflers.php

The Turbo and Turbo XL mufflers are general replacement. The Pro XS line is designed for performance.

One thing that became very clear while I was dealing with a damaged exhaust system without tips is that the majority of the performance exhaust system market these days is for sport-utes and trucks. All of the aftermarket tips that I have seen would look right at home on a pumped-up CJ5 or Bronco, but not on a Cadillac. This includes Borla's tips, which are all straight-through with clamps. The Cadillac tips begin with an inverted Y that very quickly enters two welded dual-wall, air-cooled chrome dual-oval tips. The dual tips are more than cosmetic. The inverted Y reduces higher pitched sound out of the tips by reflecting most of it back into the system where the mufflers have a second chance. Something like that is a major custom fabrication job. The stock Cadillac tips are heavy duty and top-notch, and I recommend using them from your old mufflers.

There's a good market out there for Corvettes, Mustangs, and Hemis in sedans too. Cadillac has about 2% of the overall market share, so we're in there. You can gauge the market cash flow by looking at the cat-back systems currently in production, and they are for late-model hot sedans and roadsters, sure, but the bulk are for, uh, trucks. So, it's going to be hard to beat the stock tips with anything you are likely to find in the aftermarket, or so is my experience lately. If you do find something out there that has the inverted Y, the dual-wall air cooling, and reasonable appearance for a Cadillac, let me know.

There's absolutely nothing wrong with the design and performance of the Northstar exhaust systems. The main design criteria that we have to work with is the necessity for Cadillac quietness in all but WOT driving conditions in the cars as deliverd. Borlas would never do on a hearse in the Bible Belt, to give you an idea of what I'm saying here. We can move that design point over more to a sport sedan by swapping Borlas for the stock mufflers, and leaving everything else alone, with the possible exception of low-restriction cats for those who want the utmost at the very top end of the RPM range -- which I guess is a lot of us.

My local Cadillac dealer offers Borlas as a dealer option on new cars, and will install them on any Cadillac, new or used. They don't say which ones and I haven't asked, but I recommend the Pro XS series for *T* Cadilacs (ETC, STS, DTS, etc.) because they're the Borla performance line for street cars, not the general replacement line, and I find the exhaust note subdued and pleasant, and so does everyone else that has heard it.

[GreenMachine]

I don't think that your grasping that it seems the 98 deville does not have the dual tips y split. Just a single piece of pipe it appears cut back enought to be hidden and the bottom part of the bumper is just cut for single piece.

I was thinking about using CTS tips (if I turns out I need tips, might just need some pipe and no tip) because they look pretty good and arn't outragous like some of the crazy ones I've seen.

[Cadillac Jim]

It's also possible that I'm wrong and the tips don't affect the exhaust note appreciably. They are hard to find and expensive, and if you don't have the split tips, I would use what you have. I would try the Borlas with the stock ends, whatever they are, and if you detect a hint of harshness or high-pitched sound, then go get the tips with the inverted Y from used STS mufflers.

[GreenMachine]

Alright sorry if I seemed somewhat angry in my post last night...I was ..Sabres win streak came to an end...anyway this shows what the setup looks like:

Click to make bigger:

A chrome tip would enhance its look, the key is not making it pretrude to much from the bumper and just kinda be a truely a tip or lip, just enought to make the end look abit nicer. Althought right now from behind you can't even see the muffelers which gives a clean look that I kinda like. The cars pretty dirty from all the peices of trees and such that I've had to drive over the last few weeks. Thos dual tips wouldn't fit, however it looks easy enough to cut/modify the piece to make them fit, but the key would be making each side equal and look good and not a "barn job" so to speak.

Also it does appear my mufflers might have some rust holes in them (that might be a side effect of when on my trip I hit a large unmarked contruction bump at 70 and I heard something scrape in the rear, might have taken enough of what ever they are coated with off to allow for rusting right threw. Holes are small now (if they are holes) but that would certainly make the car louder.

[Cadillac Jim]

There are (at least) two ways to eliminate that last trace of harshness in the exhaust note: An inverted Y and dual tips like the Cadillac Touring packages, or angling the pipe down at the end like your very clear photographs. I would use the stock tips from your car and forget the chrome tips, and keep the stock look.

Years ago I had a tricked-out Chevrolet small block in a family-looking Impala station wagon that had a boss exhaust note, a standard shift, and idle of 1200 rpm, and a very slight whole-car body shake at idle. At a long light, sometimes people would start to look around to figure out which car was making that noise. When I noticed that, I would look around for it, too. I love a sleeper. I would keep the stock look. And, I would use your existing ends, because that last bend isn't free, and it's necessary to keep your bumper cover clean as well as having a minor silencing function.

Again, your symptoms sound more like an exhaust leak behind the cat, which is easily fixed for little or nothing in a few minutes. You may decide to do nothing at all.

[JasonA]

Two things of note:

1) The exhaust construction must have differed from what went into the 1997 sales brochure, because it clearly states "stainless steel exhaust". Maybe that doesn't mean that the WHOLE system is stainless, but I would at least expect a part of it to be.

2) The inverted Y with dual tips (quad tips, if you include both sides) wasn't installed only on the "Touring" cars. All Sevilles had them (SLS and STS) and all Eldorados had them (Eldorado, ESC, and ETC). None of the DeVilles had them through 1999. All DeVilles had them 2000 and beyond. I don't know if they do anything to enhance performance, but they sure do look classy.

[Cadillac Jim]

The tips that include the inverted Y would likely have a slightly mellower exhaust note with performance mufflers but this is pretty much wasted with the very quiet stock mufflers.

I always thought that my exhaust was stainless steel, too, until I saw it. My 1990 Grand AM Quad 4 HO was supposed to have an oil cooler, too, but it didn't. They dropped it early in production, and the fittings weren't even on the radiator that came with the car. The oil cooler was on the 1991 and 1992 brochures, too. You could buy the parts and put it on (oil filter adapter, fittings, hoses, radiator) but it didn't come on the car.

Perhaps I'm wrong and my system is stainless steel. However, I did see a lot of pinhole rust on the cat-back pipe.

I'll be all over the car in a couple of days, making sound bites for uploading here and taking pictures of the installation. I'll get some close-ups of the stock parts while I'm at it.

[GreenMachine]

Thanks for the intrest guys. I too will take some pictures of the car before and after shots of the mufflers (if indeed I do need new ones).

It might not be this week, or even next. The car is going in for some painting because someone keyed it from the left turn headlight, driver door, to passenger door, and stoping where the rear wheelwell begins, front bumper cover is getting replaced since the bottom part has cracked from being brittle and my father hitting a high parking curb that was under some snow, rust is forming around the rear license plate holder and getting that taken care of before it decides to spread and rust threw the trunk).

Basically its a big job and the car is going to look great, so I want it to sound and perform just as nice as it looks Another thing to add to that list is a tire rotation and oil change, checked the percent today and it told me 13% Oil Life Left Also I have read that there are some greasegun fittings on the front suspension/control arm areas that needs greaseing or premature wear of tie-rods and bearings could occur, so I'll have to take care of that cause I don't remember every doing that but the FSM tells me that should be done every 6months or so.

[JasonA]

EGreen, there is at least one 97-99 DeVille running around here with some very subtle chrome tips on the exhaust pipes. I am NOT a fan of the cheesy chrome tips you can buy at Pep Boys, or similar, but these extend from the bumper only 1/2" to maybe an inch. They merely illustrate that the car has dual tailpipes and it looks very clean in my opinion. I have no idea what they are, or where he got them (I've only seen the car in motion, and just a few times), but those DeVilles look great with very mild shiny tips like that.

[GreenMachine]

Car is back from paint, looks great, unfortunately insurance company, and policy, didn't allow for us to force them to pay for an OEM bumper on such an "old" car, but the after market fits good, body shop guy did a great job of making that fit. Its not show car quality at the seams but nearly as good as it was originally. To the untrained eye (and people not looking for fit problems) its not noticeable.

Key scratch gone and new pinstripe matches other sides great. Rust that was forming around the rearverse light/license plate and rear trunk emblem have been fixed along with some initials "SS" someone scrapped into the trunk paint.

All in all very happy, pictures to come soon, later this month once the paint is totally cured I'll have some great wash and waxed shots. For those of you in the Buffalo area, if you ever need show car quality painter, send me a PM.

Anyway on the muffler subject, I decided to let the shop I usually take the car to do the oil change since I've been so busy, the weather has been so bad, and the car was chirping ot me on startup "Change Engine Oil" (had ticked to 9% on the way home from the body shop and we usually change well before that out of convenience, but its nice to know how far you can really go)

Turns out my left muffler has developed a hole, that is getting bigger, I was quoted a price of $180-$190 for an OEM replacement (in parts alone). Since from that one link to a place to buy Borlas I can get 2 for $150, that is the route my father and I have decided to go. I'll have more information on that once we order and have the mufflers in hand.

[Cadillac Jim]

Get the Borla ProXS series. Mine are part number 40357.

[KHE]

Car is back from paint, looks great, unfortunately insurance company, and policy, didn't allow for us to force them to pay for an OEM bumper on such an "old" car, but the after market fits good, body shop guy did a great job of making that fit. Its not show car quality at the seams but nearly as good as it was originally. To the untrained eye (and people not looking for fit problems) its not noticeable.

Key scratch gone and new pinstripe matches other sides great. Rust that was forming around the rearverse light/license plate and rear trunk emblem have been fixed along with some initials "SS" someone scrapped into the trunk paint.

All in all very happy, pictures to come soon, later this month once the paint is totally cured I'll have some great wash and waxed shots. For those of you in the Buffalo area, if you ever need show car quality painter, send me a PM.

Anyway on the muffler subject, I decided to let the shop I usually take the car to do the oil change since I've been so busy, the weather has been so bad, and the car was chirping ot me on startup "Change Engine Oil" (had ticked to 9% on the way home from the body shop and we usually change well before that out of convenience, but its nice to know how far you can really go)

Turns out my left muffler has developed a hole, that is getting bigger, I was quoted a price of $180-$190 for an OEM replacement (in parts alone). Since from that one link to a place to buy Borlas I can get 2 for $150, that is the route my father and I have decided to go. I'll have more information on that once we order and have the mufflers in hand.

Did the body shop have a bake/cure setting in their paint booth - it cures the paint and you can wash/wax immediately. The chrome trim that surrounds the license plate and backup lights on the '94-'99 Devilles seems to trap dirt and crud and then rust begins. It is probably best to clean behind the trim on a regular basis - especially during the winter months.

Did you check www.gmotors.com for OEM mufflers? They will do MUCH better on price than your local GM parts counter.

[GreenMachine]

yeah I did, after their 20% above cost markup its about the same, gmpartsdirect, and rockauto all had high prices, that fact of the matter is OEM muffler stuff is always expensive. So I may as well "upgrade"

Well the shop said to be on the safe side (because there was such a large area to be painted) that I shouldn't put any products that could inhibit it from curing. They did say I could wash till my hearts content though So I'll take some nice sunset shots, I tell ya, even without wax the finish they put on the 98's looks great.

[KHE]

yeah I did, after their 20% above cost markup its about the same, gmpartsdirect, and rockauto all had high prices, that fact of the matter is OEM muffler stuff is always expensive. So I may as well "upgrade"

Well the shop said to be on the safe side (because there was such a large area to be painted) that I shouldn't put any products that could inhibit it from curing. They did say I could wash till my hearts content though So I'll take some nice sunset shots, I tell ya, even without wax the finish they put on the 98's looks great.

OEM exhaust is expensive but it usually lasts 10+ years. I think you get what you pay for in that respect - All three of my Cadillacs still have the original exhaust components on them.

[GreenMachine]

the Borla million mile warranty is good enough for me.

Anyway now I'm getting kinda concerned that something else might also be wrong, my driving has been "normal" and the usual conditions (minus heat, its been cold lately) and my MPG is all they down to high 12's now. I haven't even done any WOTs or anything. No codes indicating any problems (do have as history but those seem to be ghost codes as the car runs fine and my FSM leads me to believe there isn't a bad problem as I don't have the symptoms its mentions).

02 sensors maybe? I'll have a look under the hood and make sure all sensors are plugged in. Getting a little concerned now. Maybe my cat is on the way out, (I do hear a rattle sometimes, the guys at the shop said it was internal to the cat and I shouldn't have to worry about it for awhile). car runs just fine except for terrible MPG.

Never really thought a hole in the muffler would cause this, would it? ifs its getting clogged I suppose it would. Hmm. I'll have to ask my dad/brother if they idle it in the morning before going to school, thats a sure way to get it to drop....that would also put my mind at ease a bit.