P0420 P0430 exhaust y pipe question.

I have a used 2013 DCSB Tacoma 4.0l manual 6 speed. I bought it with the TRD supercharger installed with a URD MAF simulator, DT long tubes, and O2 simulators. It has 50,500 miles on it and about 35-40,000 on the Exhaust and Supercharger.

My problem is I countinue to get codes thrown. My Ultra Gauge reads them as P0420 and P0430 occasionally it's is just one code sometimes it is both codes. I'm running about 12 in the A/F ratio 10.5-11 at WOT 12-13 at Cruise (Wideband A/F gauge) I talked to Gadget at URD but no true solution was found for the codes. The Y-pipe that is currently installed is a mix of aftermaket cats and stock Y-pipe. I have checked for exhaust leaks via the hose to ear stethoscope method and have nothing.

After much research I have a grasp of the use of the front and rear O2 sensors monitoring the health of the cats which is what the O2 sim is designed to adjust and prevent a CEL being thrown. I need a new Y-pipe cause it's a choke point in my exhaust.

Here is my question if I was to move my rear O2 sensors to behind the new Cats on the Y-pipe this would mirror the stock system of O2s in front and behind a cat. Would this be more effective then the O2 sensor sim and stop my cat inefficiency codes? Or would doing so create other known issues. Is there a difference between the front and rear cats on a Tacoma or are they the same material? My idea is that the ECU and O2 sims would work correctly and other a cat sandwiched between them. Just a foot or so further down stream of the exhaust. Feed back and thoughts appreciated. Also no fault on URD or Gadget he has been great.