Exhaust recommendation

GoliathAT4 · Mar 1, 2026

Hi all! Just got my 26 AT4 6.6 gasser. I've been researching on which cat-back exhaust system to put on it, so I thought i'd come here to see what other have installed, likes dislikes, etc. I've been looking at the Flowmaster Flow FX, but wanted to see what others think about it etc. Thanks!

john151ama · Mar 1, 2026

I have the 6.6 gas as well on my 24 AT4X. I put on the Borla system. It is available through GMC but I bought it on line from another vendor for about $400 less. I installed my self in the garage in about an hour. Cut the stock system in 3 pieces with the cut off wheel to pull out easy. I love the sound, just what I wanted. Nice throaty V8 sound, no drone on the hwy. It is a little loud on start up. When I remote start it outside I can hear it inside until it idles down. Very pleased overall. I did the black tip option as I got rid of all chrome on the truck. Everything is holding up well so far.

gemarsh · Mar 1, 2026

GoliathAT4 said:
Hi all! Just got my 26 AT4 6.6 gasser. I've been researching on which cat-back exhaust system to put on it, so I thought i'd come here to see what other have installed, likes dislikes, etc. I've been looking at the Flowmaster Flow FX, but wanted to see what others think about it etc. Thanks!

Welcome.

shrubs2000 · Mar 8, 2026

GoliathAT4 said:
Hi all! Just got my 26 AT4 6.6 gasser. I've been researching on which cat-back exhaust system to put on it, so I thought i'd come here to see what other have installed, likes dislikes, etc. I've been looking at the Flowmaster Flow FX, but wanted to see what others think about it etc. Thanks!

I just went the muffler delete route. Not my truck but here's a video