I got a 02 Z28 with Long tubes and offroad y-pipes. I dont have 02 simms. Could not having any 02 simms cause the car to "funny" i.e. not produce as much power. It has already set off a light just wondering if that could be why I am running rich. Speaking of rich could not running any simms cause the car to run rich?

 

If you haven't tuned the car after the header and ory install then that is likely the reason you are running richer. Only thing O2 sims to is trick the PCM into thinking the cats are still working properly. Get the codes scanned as that will be one of the codes are could be setting off. Did you remove AIR? If not then did you get restriction plates so you won't burn up your Air check valves (can't remember what they were called right now).

Anyways get the codes scanned (Autozone) does it for free and write them down and post them on here...the guys will let you know whats going on.

 

O2 simms only trick the car into thinking you have cats, and thus, not throwing a code. So basically, O2 simms will cause you not to have an SES light. If you had cats before, it will seem like its rich from the smell, when it actually may not be. Mine isn't, but still has that gas smell from the lack of cats. However, running rich does usually happen after a header install. I am not sure why people even get O2 simms... Since they should get the car tuned anyways to lean it out, the O2 codes can be deleted at the same time, saving you some money.

Basically...no, not having O2 simms will not hurt performance. I didnt have any for about two months, just an SES light.

[EDIT]: Oops, a little late, oh well