I put a dc 4-1 header on my car about 2 months ago and now i'm having a check engine light come on. I took my car to the dealer and he said that the engine code was a p0133 and that my 02 sensor was miss reading. He said that because of my performance upgrades the computer thinks there is a problem because it is using extra fuel. I called up dc and they said it could be a wiring harness any ideas? I also have a new 02 sensor that is less than a year old.