Originally Posted by V8Slayer
A quick and cheap way to avoid the dreaded P0420 is to use 2 spark plug fouler's(http://www.oreillyauto.com/site/c/de...0259&ppt=C0334
) to move the rear O2 sensor out of the exhaust stream. Most people seem to have good results with this method(myself included) and only takes a few minutes to do. Just drill out the bottom of 1 fouler so the O2 sensor can fit inside screw them together and then insert back into your exhaust pipe.
This works on 04 and earlier systems bit in 05 the Efi system changed and doing this will not only screw up your closed loop fueling but it won't get rid of the PO420. If you do this to the Front O2, it will really mess things up.