AFE Diesel Exhaust GMC Sierra 2008. Arm your rig with the AFE diesel exhaust Large Bore system and pull the trigger on restrictive factory exhaust. AFE scraps that stock peashooter for this high-caliber cannon that blasts hot gasses from your tailpipe with a vengeance. 4"mandrel-bent tubing and a straight-through muffler keep EGTs low and performance high. Already famous for their cold-air intakes, AFE is no stranger to diesel performance. With the crosshairs set on your tailpipe, the AFE diesel exhaust Large Bore system locks and loads your rig for wicked horsepower and torque gains. The Large Bore kit also lets you custom tune your exhaust note. Mount the muffler one way for a powerful growl; reverse it for a mellow rumble. And hang on, because this muffler's 8"diameter delivers a powerful kick. The kit works with any cab/bed combo and includes everything for an easy install. With your choice of 409 stainless or aluminized steel, the Large Bore kit also works with any budget. And, your AFE Exhaust is backed by a 2-year warranty. 2008 GMC Sierra AFE Diesel Exhaust. Exhaust, Mufflers&Tips, Diesel Exhaust Systems .