[buzzinhalfdozen]

First thing you should find a friend with a scanner and see which cylinders are miss firing. If you can't find one I've seen alot of plug wire issues with these engine particulaly the ones going to the rear cylinders, they go open quite often. I don't know where you're located but around here (G.M. garage) we have a flat fee for a road test using a scanner (80.00) most times the issue can be diagnosed fairly quickly and most important correctly. Spend a few dollars and have it properly diagnosed, replace the correct part or parts the first time and actually save your self money. Joe