I don't know if it was this board or the nasioc, but someone had listed an O2 Sensor Adapter that screwed into the rear sensor boss to pull the sensor about 1/2" back out of the cat to deal with the PO420 code.

 

If anyone knows where I can pick one up please let me know. Thanks.

I dont know about this O2 sensor, but most seem to have the same thread-the same as the larger spark plugs used on many cars. I found out the hard way when the O2 sensor on my Nissan truck left half it's threads in the manifold, and I was able to use my spark plug thread chaser to clean/retap the hole. The point is, if that is the case for yours, a Spark plug non-fouler, available in the "Help" section of any autoparts store would do what you are looking for.

 

Now, as far if it produces the desired result regarding getting rid of the code, I am not sure if that is going to help or not. If the sensor is defective it may need to be replaced-some sub's are under recall, let us know how you make out.