97 accord f22b1. NA, cold air, header back ex, Ok heres my situation, when i installed my exhaust system, just about everything went together and lined up with the factory mounts like it should, except for the 02 sensor ports. My stock exhaust had em directly on both sides of the cat and the new system has the up stream sensor right in the manifold. i can probably re route some wires and make it work But Im thinkin that the stock ecu is going to over compensate for the surely higher voltages that the sensor will be sending from being that much closer to the motor.

 

nope. you can put it anywhere between the cat and the head. the stock O2 isn't that accurate to begin with, it won't make any difference.