I have spent 2 months and way too much money chasing after a random miss during acceleration and when cruising at 55 mph. After all this time, I finally broke down and took it to the GM dealer. They looked at it for two days before they traced the problem to the replacement cap and rotor I bought from Autozone late last year. This is just informational, and I may have put it in the wrong forum. Think about this next time you get a P0300, hesitation while cruising at 55 mph, or hesitation at 2000-2500RPM.

 

Yep, poor quality aftermarket parts can definitely cause these problems. Glad you got it fixed even though it took a trip to the dealership.

 

Yes. And thank you for your help. I just wanted to post this (though it's embarrasing) just in case someone does the same thing maybe they won't have to replace their intake manifold gaskets without good cause.