thats exactly why theres no o2 bung cuz its an egay generic "high flow cat" but in reality its not even a catalytic convertor its just a test (straight) pipe with a shield over it. hope you dont have emissions in your state cuz you will most def. fail. but if you dont have emissions then having the test pipe wont hurt performance, but not having the 2nd o2 in may. you just wont be filtering any of the exhaust gas. some ppl have said that with test pipes they get more sut on their rear bumper and some have a rotten egg smell to their exhaust.