Recently my 2011 mustang Gt has been tripping the P0430 code. I first checked for leaks. I replaced the exhaust clamps since they were loose regardless of how tight I torqued them. No luck, code came back. I then replaced the downstream O2 sensor on bank 2 thinking it would solve the issue. Nope, code came back. With 216k miles on it, I figured it was the cat. Replaced it and still the code returned. The cat was a Walker from rock auto. I then don’t replaced the upstream O2 sensor, spark plugs and the cylinder head temperature sensor. Still no change, the code comes back. Not sure what could be causing it. Anyone have any ideas what it could be?