I've got a 2007 Dodge Ram Quad Cab with a 5.7 Liter Hemi in it. It has 52k miles on it. I just had dual exhaust installed, behind the cats & oxygen sensors. The cats or oxygen sensors were not tampered with at all. However, after driving approximately 40 miles, my check engine light came on. The code pointed to a cat failure on the #2 bank. Several people suggested I wasn't getting enough back pressure. Several solutions were offerred up, all of which I am very greatful. I wanted to let everyone know how I finally fixed the problem.

A PINHOLE - After all of the attempted fixes, the problem turned out to be a pinhole in a weld. Back pressure, or the lack there of was not the problem as originally thought. I finally got a suggestion from an old exhaust guru who said that a having a pinhole was the biggest problem he has seen causing a check engine light following exhaust work. Sure enough, mine had a small pinhole at the first weld. We fixed the pinhole and no more check engine light. Thanks for all of the suggestions. I hope this solution will help in the future.