Im sure if they put a tester in the exhaust, your car wouldn't pass. I have never tested an OBDII car, but i heard they just plug into your computer and since being OBDII it has a sensor for just about everything on the damn car. lol Such as your rear O2 sensors checking to see if your cat converters work. The MIL's Eliminators changing the voltage (or whatever) reading to the computer to make it think that the cats are present and working fine. It would sure be nice if it would pass with the o/r pipe on there. Cuz I've got a mac O/R H pipe, its too much work to change it to do emissions if you ask me lol