[StealthSonic]

Hi Accord pros, I've installed an OBX 4-2-1 headers into my 4 cyl 2000 Accord for over two years now, but it finally gave me the engine check light. I'm not sure where to start to trouble shoot the problem. I'm pretty sure that it's the header... I'm getting some of carbon builds up on the sparkplugs' tip.

Could it be that the catalytic converter have gone bad?
Or O2 sensor gone nuts?

I have the check light on for over a year now, the light do accationally went off but it only off for like a day. Other than that the car runs flawlessly.