I realize that with Long Tubes comes common O2 codes. I have had these headers a long time and no problems so I need to rule out a few things I have a misfire in the motor while going down the road after the motor is about halfway warmed up. It last about 5-10 seconds and then is fine. The codes are PO1153, PO135, PO154. I run O2 extenstions and Simulators for the rears. I have about 35K on the car.