My car is OBDII, so I have two o2 sensors. One before the cat and one after. I started getting a CEL when I put on my header. It was made for the D16Z6 and I have a D16Y8. My factory o2 sensor is at the top of the exhaust manifold, but the header has it at the end of the header. I had to lengthen the wires quite a bit, and since then, the CEL goes on. I pulled the code at an automotive place and it says Slow Response From O2 Sensor. Once reseted, the CEL would come on about once every two weeks. Now I put on a high flow cat. The problem was the O2 sensor bungs were in front of the cat, so my first and second O2 sensor are right next to each other. I did some research and found that the first O2 sensor is responsible for making sure of the 14.7:1 air-fuel mixture is correct and makes adjustments based on it's reading and the second O2 sensor makes a comparison to see what the cat burns off. What should I do? I believe the engine just goes with a generic air-fuel mixture when it can't get a reading from the O2 sensor. And VTEC still kicks in, so the CEL isn't affecting that fortunately. Everything runs fine. But now I have a constant CEL on from the O2 sensors. Is there a way to bypass this at all?