So what would happen if I took off my muffler for a race event and left the cats and everything else on? I would be doing this just to save some weight on the track. Would this negatively effect my performance of my car?
The O2 sensors aren't apart of the muffler section, so it should be fine for no CEL, however I agree Bngl3rt in that exhaust gases expelled out underneath the car (straight out from the cats) could be dangerous.
It'll also be really really loud and you'll probably loose some low end torque.