NTK replacement oxygen sensors work well if you do need to replace your rear O2's. You will definitely have to try the anti-foulers, most decent auto parts stores should have them. You may have to modify and/or drill them out and possibly stack more than one or stuff some steel wool in them to get them to work right. I ended up putting my stock SRT8 manifolds and cats back on my car to get through emissions, but it was that both my rear O2's were bad also... *shrugs* So that being said, Try the non-foulers/anti-foulers trick, or get rear O2 simulators possibly? If you have an older rev crom on your predator v9r18 or earlier, you can still turn off the rear O2's but it will not set a readyness code for them so you still won't pass an OBDII scanner. I went away from the headers all together and just made some cat-less mids I plan to use when not doing emissions and swap back when I need to get through emissions again. I know my car will pass with the supercharger and the cats and canned tune from Vortech. Custom tune and cat-less mids is for the rest of the time! It is 3 drive cycles to set the readyness codes, give or take, from my own experience. Good luck!