My check engine light was on so I had the codes pulled, and this is what I got. P0440A evaporation emission system solenoid, P0420A catalyst low efficiency bank 1, P0430A catalyst low efficiency bank 2. I'm guessing that the catalyst low efficiency bank 1&2 codes are the o2 sensors. I could be wrong. The car is a 2001 Z28. Any information you could give would be helpful. Thanks.

 

Could also be cats; believe gm extended cat warranty on some year fbods, so it could still be covered. As far as the p0440, read here how to check your purge solenoid, and also a pic of where it is on intake if you click the further link in post #5: https://ls1tech.com/forums/general-m...ing-often.html

 

Those are codes for the cats not working properly. I think the extended warranty on the cats is to 100,000 miles IIRC. I had the same problem and the dealer fixed it for free.