I haven't had stacks on mine, but do have a 4 inch straight piped exhaust, I had a mbrp muffler in mine before that came with my kit, and it was really quiet. Could just about talk next to the truck with it running, unlike it is now. Don't know if a muffler like that would help with stacks, but I do know that it took alot of the loudness out of mine when it was under the truck.
Congrats and best of luck