Bolts from the cartridge to the rear exhaust housing are hard to get to. I had 2 missing (only had few months) you sure there all tight ? Ford didn't wanna do mine under warranty due to I got it serviced elsewhere, tried to charge me 1000 to tighten and replace two. Took it out myself and the housing bolt holes had cracks in the bolt holes as well as the flapper hole. I'd be triple checking, exhaust place near me wanted $150 an hour and wouldn't give a rough quote.