I'm using this exhaust, Flowmaster 17392, with this y-pipe with cats, Flowmaster 2010019 - Flowmaster Direct-Fit Catalytic Converters

It sounds great. This is on a 5.3 in a 1992 short wheel base single cab. It is all designed for 2000-2006 truck. It all fit fine besides having to make hangers. My truck is lifted though. The y-pipe does hang a bit lower than the stock 92 pipe did.