1999 Pontiac Firebird 3.8L got about 190k miles on it?

Ethan replacing parts is 90% of the time is not going to correct your problem.As you know pep-boys would replace a ton of parts and hope for the best.What you need is a pro drive-ability tech that works on these engines everyday and has the training and proper tools to find and fix the problem period.Any good chevrolet or buick dealership in your area has a pro drive-ability tech that in a short time can find the problem and tell you how much it will cost for parts and labor.They will also give you a good warranty for the repair.In the long run this will save you good money over guessing and replacing good parts.Best of luck with your firebird.