Dreaded head gasket?

[don_k]

I have an 02 Deville DTS (vin 9) that I bought in 2007. It had 84,000 mi and 3 months of GM warranty left on it. I immediately noticed temp spikes on long pulls (uphill or accelleration). I took it to the dealership, they diagnosed and testdrove it - said there was nothing wrong. The first trip I made across the California desert (I-15) the temp went to the last tick before "hot" and the air conditioning cycled on and off. After this the trans would not lock the TC. I took it to the dealership, they repaired the trans and again said the engine was fine. It is now out of warranty. I have installed an aux trans oil cooler, new hoses, new thermostat, new waterpump, new radiator, and an engine oil cooler. It does not use or leak coolant. It continues to have temp spikes on long pulls. They are worse with increasing outside air temps (noticable at temps above 70 deg) below 70 deg the spikes decrease to not noticable on the temp guage at 50 deg or lower. Is this the beginning of the dreaded HG problem?