I have had car for 2 years. I had a mis fire problem in March this year which was fixed. Got a P0430 code after - managed to get replacement cat for bank2 from on line breakers in England. This was replaced - old cat in bits inside, everything ok for few months until I got P0420 dtc. Replaced cat on bank 2 with another one from breakers - still getting same code and wondering if O2 sensor problem?