Hey, I have a 2012 kia soul 1.6 standard transmission. I've been having the same code popping up after each part replaced. So far we've replaced the knock sensor, the MAP sensor, all four spark plugs, the upstream and down stream 02, and the p0420 and p0420 p, keeps coming back. I hate to guess but I'm thinking the Cat may need to be replaced? Not sure what to do. Any thoughts?