Hello I have a 1.8 valvmatic avensis 2010 . Recently over the last 3 days I have had these 2 codes come up . First p0420 so I put some cata clean in with the fuel and seemed fine then I today p0301 missfire cylinder 1 . I have tested the o2 sensor and it's switching back and forth rich and lean also the temp of the cat on the scanner but I'm struggling to understand the readings there's 2 cats or sensors on 2 parts of the cat ? PLS see pic below