[GST97ORL]

Second O2

You're right in the respect that it IS there to make sure the cat is present and working correctly. The most commonly referred-to method of secondary O2 sensor fooling when using a test pipe is to somehow attach it to the outside of the pipe so air gets to it, but do not unhook it from the ECU. Of course, you'll have to weld up the area where it was. I personally do not know if this method works, because I still run a cat. But many people have said this method is working for them.