GMC Sierra For sale: Catback kit for Sierra, original Fox muffler, Skyline. 3 inches, no back pressure at all. Goes 140 while closed, doesn't suffocate or harm. Custom made for the exit, and the exit is factory. Custom made by Ben Mardah, and the kit is a full 3 inches. Its sound is quiet and its tone is nice, and if you close it, it makes no sound. Note: It has been used minimally and without a device, and I don't have a sound for it. I won't disagree with the serious buyer. The sale is urgent.