Don't Know What To Do Next!!

I have a 2000 Grand Prix SE, 3.1 engine, 152,000 miles. It started running rough, jumping and sputtering at low speed under load at first, but now it does it going 55 mph and up. Changed the intake gaskets, head gaskets, plugs, plug wires, checked the MAF, had a vacuum test ran on it, changed fuel filter, checked air filter, changed PCV, tried fuel treatment...nothing has worked. It runs fine until the engine gets warm. Seems to miss a little during idle, too. Could anyone tell me what my problem might be? I don't know what else to do. Thanks!

It sounds like you could have an issue with the coils and the ignition module. Sometimes when the engine module gets hot it will start causing issues. Try one from a wrecking yard for your particular car. They are fairly inexpensive second handed and may solve your problem.

I'll call around and see if I can find one tommorrow and see how that goes. I really appreciate it!