I installed an OBX header today off a 04 tiburobn, it was a pain! i finally got them on and custom fit the downpipe.... to the resonator... yea we had to cut the cat, at this point there was no turning back! So i was able to fit both oxygen sensors on the header, one on the top and the other at the bottom. It performs very well now with my exhaust and intake but has a sound to it that im not real sure i like. after 2 hours of driving the check engine light came on and im thinking of getting a spark plug defouler tomorrow and doing it this way, any other advice guys?