:cry2: Ok first off im really new to this forum thing so bear with me hear, i own a 00 civic si and i put a dc sport 4-1 header on it, well shorly after that the damn check egine light came on. so i went and had it checked out and the code it was trowing was like a p420 or something dont remeber but it said it was catalytic under thrush hold bank 2 I dont know what the hell that means and ive had a new cat, put in there last year. but the real problem is when im drivin the car. just going along 60 and 75 mph the car just stright up starts falling on its face just boggs donw i give it more gas and it jumps up and runs fine does it like 2 times and then runs fine some times i just let off the gas and it will do fine to, but you can stick in the clutch and rev it up revs up fast and with out proplems so if you need anymore info i will gladly answer any questions. I DONR KNOW STUMPED. any info would help!