First of all I'm new to the forum and wanted to say hello to everyone. This is a great forum with tons of great information. I was just wondering about the differences or pros and cons to having a cat or "performance" aftermarket cat on your exhaust system. I was also wondering how many of you guys run with an aftermarket cat on your trucks. I'm toying with the idea of running 4" straight off the turbo with a 5" tip or just 5" straight off the turbo all the way back. I'm just trying to figure out if I want an aftermarket cat or nowt. I did a search about it but didn't find much about 5" exhaust. Any information or insite would be great. Thanks Chris

I also have been searching for a aftermarket high flow cat or buying a used D/A cat and making it high flow, and having it made Hi Flow by a aftermarket cat manufacturer I know of. The only Hi flow cat I have found is for the 6.5, although there is one made for a 6.5 4" system. Looks small, has a 2.5 year warranty and is fairly cheap. I had a aftermarket hi flow cat on a gas suburban a few years ago and it really did improve flow, mpg, and temps.


A forgot to say that I sold it to a guy in California and it passed emissions 2 years after I installed it.Edited by: gardnerteam