Well FOR OFF ROAD USE / TRACK USE ONLY, if the check engine light bothers you when you are OFF ROAD / TRACK USE ONLY, than go on ebay or your preferred source for cheap chinese goodss and purchase a 90 degree elbow fitting that goes between the post cat o2 sensor and the downpipe that way you will trick your car into thinking that your cats are clean because it will be out of the exhaust stream and the voltage will read errr either lower or higher, i forget the way it works but thats what i did in my old E46 with ebay race headers when i went "OFF ROAD/RACING COURSE TRACK"
