I have a 1990 Pontiac Grand Prix with the 3.1 MPFI v6, has 103,076 miles. It has a new fuel pump and filters, newer battery, newer Alternator, new coil packs and ignition module, plugs wires, IAC. The car runs with a mis fire i cant seem to figure out why. The hotter it gets the worse, trys to stall sitting still. Car has all the power in the world on the highway. Today I disconnected the battery for 20 min, drove around and around trying to reset the computer, ran terrible then improved to its normal self. Parked for 30 min, went out started it up ran perfect, no miss. Drove some more, problem came back. Also the problem gets worse with turn signal. Thanks I pulling my hair out trying to find the issue, please help!