Hi, my name is shawn. I have a 2008 mitsubishi lancer with about 30k on it. I purchased a SES1835TT-1 from injen. I got to bolt it on and found some missing bolts and hanger for the added bracket provided with the kit. I got it all on and had a p-0420 code and still heard a exhaust leak. A little more investigation found a bad donut gasket. I replaced the donut gasket and it sounds a ton better. I still get the p-0420 code. I have had a couple of people along with myself crawl under the car and try to feel for an exhaust leak somewhere, but we all feel nothing. I am wondering if the new cat and the, I don't want to call old, o2 sensors are not compatible? I have tried to contact the company but they have no information for me.