Ok, I am having a very aggrevating problem with my 95 Buick Roadmaster. As with the Impala SS, it is outfitted with the LT-1 corvette motor. In the cooler months, it is amazing how fast this 4500 pound bohemouth gets moving. In the warmer months, it changes it's ways. The problem is a missing type of sound and hesitation. It is speratic. Sometimes the car runs just fine. If it has been sitting out in the hot sun all day, it is almost always bound to have the problem. Of course, running the A/C just intensifies the situation. It has been in 3 Goodwrench dealers, and 2 private garages. I have had almost everything replaced, and the problem is still there. The shops fix something and say it is fixed, then it starts doing it again on the way home. They have replaced the sparkplugs, plug wires, distributor, coil, catalytic converters, fuel pump, fuel filter, EGR valve, MAP sensor checked, and cleaned injectors and plenum. None of these have fixed the problem. The sparkplugs were replaced again, because they showed carbon striking (?). I have used octane booser a couple of times, and the car will run fine for a tank or 2, then just go back to missing. I tried just using the premium gas, but that did not make a difference. The problem is hesitation at low rpms. Whether I am just taking off or cruising down the interstate, it hesitates, spits, sputters until it gets revved up. Once it reaches the higher rpms, it pulls out of it, but it still has a surging type of feeling. During the winter months, it doesn't display any symptoms at all. If anyone has had such a problem or has any ideas on what else may be causing the problem, I would greatly appreciate any help I can get. Who else to ask about LT-1s than hotrodders, right?