Life with p013c CEL code

Hello, Everyone,

I've had my 2007 Jeep SRT since 10K miles. I bought it off Ebay from a Fl dealer. Within a couple of weeks of having it, the CEL illuminated. I bought a 100K mile warranty so I took it to my local dealer.
This was Jan 2009.

Dealer said it was P013 code, and replaced both rear O2s. Picked up Jeep and the light came on again. I took it back to dealer next day.

Dealer installed new computer and reflashed it. Light came on again. I took it to dealer a third time. Dealer then blamed the Magnaflow exhaust system.

I gave up. I bought a Diablo Predator tuner from local board member here and used it to deactivate rear O2s. This worked, but Jeep wouldn't pass emissions here in Texas with rear O2s turned off. Diablo did confirm the P013c code (slow responding O2 sensor right rear bank)

So I believed the dealer and bought a slightly used factory Cat-back system from another board member and tried again. I still got the P013c code.

Almost three years later and Jeep now has 50K miles on it-- and the CEL is still on.

I recently have started to fool with this thing again. I've read all about this issue on this and other forums and possible ways to fix it.

I tried O2 extender on passenger rear O2, but CEL still came on. I tried using TWO extenders on passenger rear O2, and CEL still came on.

I've sprayed the exhaust connection at cat-back with soapy water, and I could find no air bubbles (leaks).

Any ideas? I am about to try one of Big Daddy's "mini-cat" extenders to try on it. I'd pay $50 no problem to get rid of this light so I can put my Borla ex on again but I've read on some other Dodge forums where these mini cats didn't work.

I'm currently running 91CAI tune using the crom9r12 update, but it doesn't seem to make a difference what tune. I've heard that the crom 9r29 update has worked for other owners, but they have newer SRTs and I have an older model Diablo Predator tuner that won't accept anything newer than the 9r12.

Stock 2007 SRT except for the K&N filter and free intake mods.

Also, the CEL disappears when I take the Jeep to the mountains in New Mexico. It stays off for a few days when we get back to Austin. (That's how I've been able to pass emissions). Maybe this will help in the diagnosis.

thanks
greg