The O2 sensor hole is on #5 and #6 pipes to stop O2 heater codes coming up on 1999 and new cars
Mike,
Is it not true that by having the bungs in only 1 pipe out of 5, that you are not picking up potentially lean(or rich) conditions from the other 4 tubes? The factory set up collectively senses all 5 and then sends a signal to the PCM.
I remember Dan Cragin bringing this to my attention several years ago. I tried the relocated **** position for a while. It reduced the frequency, but did not stop the light on my car. When I drilled my sensors out, I put them back in the original location and capped off the relocated bungs. Knock on wood, I've only had one 02 heater code MIL in 25,000 miles.
Steve