I would check to make sure the wiring going to the o2 sensors are in good shape and not burnt or broke at the connectors. Try to check as much as you can. I really doubt the sensors are bad though.

If you could find somebody with a tuner, you could get them to turn the rear o2 sensor code off and see if that fixes your problem.

There used to be a resistor mod that you could do for the rear o2 sensor but I never could get it to work. I also think there are o2 simulators(might be called something else) that fake the computer also.

Sometimes, you can replace the cat with a high flow and they will also cause you to throw a code. I could never get our code to quit from coming on and I bought a dhp 1.0 pcm that had the o2 code turned off and fixed our issue.

Good luck with your issue though.