[PatrickB]

Could possibly be fuel injection as well. New injectors at 135k mile on mine, essentially made it perform like it was a brand new motor. Cheaper to remove them and have overhauled, than buying new. And sorry gents, a bottle of Techron ain't the same as an overhaul!

Do the easier cheaper stuff mentioned above. With mine, the issue was similar, being very intermittent, even at different rpm's/loads, engine temps, and outside air temps. Often times, I wouldn't be able to get the issue to repeat under exact same situation. Also, MPG's began to worsen... I hate just "throwing" money at an unknown problem, expecting results! However, a F.I. overhaul, if never done, SHOULD be done. Your car WILL run better, and get better fuel mileage as well.