My C6 has about 6400 miles on it. We bought the car used with the exhaust system already on. The check engine light came on about600 to 1000miles ago. We have a stainless steel GHL headers and exhaust on it and are wondering if this is why the light is on. We had a friend of ours put it on the computer and it shows emission problem. We are waiting on an appointment with our local Chevy dealer to put it on a GM computer, but are wondering if this is due to our GHL exhaust system. Is it OK to drive it this way?[/align]
[/align]Anyone have this problem or can help me out here?[/align][/align]Also, the Resonance noise inside is horrible! Very loud when your at 1500 to 1800 RPM's. Anyone else have this problem? I have sent off an email to GHL about this.[/align][/align]Your comments are appreciated! :)[/align][/align]

Well, if the car ran fine for more than about 50-60 miles with the GHL exhaust on it before the check engine light came on (i.e., the light was off when you bought it and for 50+ miles afteryou bought it, then that is most likely NOT the problem. You may have bad O2 sensors or something: always suspect that on 'vettes with headers.

The dealer may be able to fix it but my experience is that dealers usually don't/won't work well with any modifications and tend to: a) blame anything you expect GM to pay for on the mods, b) work rather procedurally and ineffectively on the problems if you are paying for it

I'd find a really good local shop that has LS1 edit and a dyno and take the car to them.

If it is the O2 sensors, ask the shop to put in dummies and maybe re-program the ECM slightly.

By the way, I have a GHL exhaust on my car ( but Kock's headers, not GHL) - they are very good, if expensive. I have no resonance -- my exhaust is a flow through and they are quite good at not having any resonance.