Just to clarify we are talking about the O2 sensor AFTER the Cat not in the manifold. You do this to one in your manifold and it will really mess things up. That adapter just pulls the sensor out of the exhaust stream so it detects less oxygen so the computer thinks the Cat is doing its job. You do that to a manifold and the computer is going to richen up that bank big time. You can find the adapters ready to install on ebay.

 

Yes the o2 sensor after the cat.