ok started off with my check engine light coming on and saying catylist effency below threshhold (bank one) and was told and was told and kinda figured it was the O2 sensor on the manifold...well i bought a brand new one and put it on and then the day later it came back on took it to autozone to have them earase it b/c i was told even tho you disconnect the battery it sometimes doesnt earase it from the computer, so i went a few days mayB a week and a half and hasnt came on...well today it came back on and im lost as to what it could be? is there anyway it could be the O2 again or mayB something else? could it be the O2 after the cat? and just to avoid questions its a 96 civic with a D16Y7...stock header