Ok, I have an OBDII test pipe with the o2 bung welded in it. I've heard that if I just wrap the secondary o2 sensor in aluminum foil and fasten it under the chassis that it will not throw a CEL. This leaves a hole in my test pipe. I was wondering what size screw/bolt would I need to fill in that hole if I removed the secondary o2 from the test pipe? Also, what if I just wrapped the o2 sensor in aluminum foil and still installed it into the test pipe. Would that work just as well?