I have a 2000 monte carlo ss with the 3.8. It idles rough and bogs down and shudders when i initially take off from a dead stop. Once it gets going its fine. Ive started taking apart the throttle body to clean it. I cleaned the MAF sensor and im getting a new IAC valve. Is there anything else i should check out before i put everything back together?

 

- if it has the factory cat, that is probably bad. GM had a large batch of bad cats in '00 and '01 (they extended the warranty on the cats, but that is now expired).
- Change plugs and wires (do not use BOSCH plugs, stick with AC Delco or NGK).