So, after changing the oil, oil filter, air filter, plugs and cleaning the MAF and PCV, I still have a P0420. Takes about 150 miles to come back after I clear it. My next plan, aside from checking for leaks again, is to clean the throttle body and replace the rear O2(s). I know that the fronts should be replaced with OEM, but is that true with the rears, too? If I go after market, any specific brand for these cars? Also, I believe this car has 2 rear sensors? (it's an H6)
