The reason I'm looking for a method of disabling the rear O2 sensor on the ECU is because my car has a weird surging effect and A/F #1 correction oscillation when in cruising RPM's around the 2k to 3k. The car has a TD04 turbo and the front O2 sensor was moved from the up pipe to the down pipe. Further research shows that moving the front O2 to the down pipe tends could possibly cause this issue since USDM ECU expects the O2 sensor to be in the up pipe and not further down. I've tried looking for anything that I can adjust related to A/F #3 on the rom using romraider but can't find anything which is why I decided to ask about the CL fueling target tables when I ran into this post while doing more research. I also tried following this post to see if I was able to adjust A/F #3 but I'm not able to find the values.
Post from a couple years ago from user "unclemat":
"The ongoing issue I had with twinscroll tune was a constant oscillation on steady throttle around 3k rpm. I think it has to do with the remote relocation of the front O2 sensor. I hope that zeroing AF3 correction limits (see this romraider thread) may help. For me the only way to eliminate this oscillation was to actually disconnect *rear* O2 sensor. "
I was considering just unplugging the rear O2 but read that it would cause the car to run in open loop all the time.
Now I know what some of you are thinking. Maybe it's a vaccuum/boost leak, injectors, gasoline, etc. I have gone through all that. Had injectors cleaned and flow tested, replaced intake manifold gaskets, replaced PCV, replaced and secured all vacuum line, smoke tested to make sure no leaks, tested using a brand new MAF, replaced air filter, tested the fuel pressure, new coils, new spark plugs. I even went as far as flashing the stock rom back on the car to see if it was an issue with the tune. I nearly gave up on trying to fix this when I ran into information that it could possibly be the rear O2. The P0420 code is already disabled on the ECU but I'm guessing that the rear O2 is still processing information regardless of the code being shut off.
Once again, thanks for the help!!