I have heard through the grape vine (mechanic/emission tester friend of mine) that you can trick the rear O2s by putting a couple washers on the sensor to get it slightyly out of the exhaust path. I have never personally tried it but all the second O2 does is check cat efficiency, so (in theory) if the second O2 reads less than the first it shouldnt throw a code.

Also, something to note is that the rear O2s dont effect performance in any way. you will just throw a code and wont be able to get through emmissions. If you dont have to go through for a while just save some money for a custom tune (typically ~$250 in our area).

EDIT: Just read about the spark plug non-fouler... it does the same thing I describe above. It should work.