I suspected that exhaust leaks might be causing my 420/430 codes. I found (3) total leaks. I plugged them up. I tried to also check ABOVE both cats but it’s hard. I didn’t see any improvement but it certainly wouldn’t hurt anything.

J-B Weld MufflerSeal Muffler Cement Plastic Tube 6 oz. ^ or search your own

Stanley – SL18116P Wet/Dry Vacuum, 6 Gallon, 4 Horsepower Black