'95 Seville STS, intermittant drops one cyl (newly acquired)

[RicknRedmond]

Car starts and runs easily.  Sometimes runs smoothly and other time runs rough, idle, cruise and power.  Sometimes smooths out while driving and stays that way.  Next start may be rough.  New plugs - Delco platinum, wires ohm check about 10K/ft all, injectors each have power to both wires, comp 130 to 150 all, fuel additive doubled - no change so far.  When running OK, just doesn't seem to pull like I expected like late ign timing.  Now these engines are built to pull best between 3 and 5 thousand, and at 4 and a half liters in a 4,000 lb car, maybe I'm expecting too much.  Here's the wildcard - previous owner had a bypass wire installed with switch "to bypass a module" to prevent battery drain while parked.  Gauges all work except that the HVAC display and settings revert to default setting if parked for more than a half hour.  Also, trip odo resets itself to zero when parked.  AC compressor also had a bypass with switch installed.  I think this energizes the compressor clutch all the time rather than allowing it to cycle on evaporator load.  It will freeze up the evaporator nearly shutting off airflow.  I don't know for sure if it's not cycling.  I don't have anything but basic electrical tools and only have a Clymer's manual.  (I'm looking for a factory manual) 

Have I given enough info here to give somebody an idea how to get it to run smoothly?  Which "module" might have been affected (needs replacement), or any other suggestions.