I installed a set of Kooks long tube headers and X-pipe with Cats on my 07 Mustang GT. Now I am getting a P0420 and P0430 codes. I used a custom tune form Brenspeed. They told me to turn off the rear O2's. However, here in New York State, they check for codes at inspection time. It will not pass state inspection with O2' off as I was told.. Does any one have a fix for this. I have just installed a Spark Plug Non Fouler into the Cat's and than installed the O2's. Not sure it this trick will work. Some web sights show using 2 of these non fouler plugs togehter. Is that needed?? Waiting for computer to go through its testing cycle to see if this will work. Other parts installed, C&L Race cold air, under drive pulleys, 430 gears.