Banks Monster Diesel Duals 4" exhaust system flows up to 88% better than stock and virtually elimi nates backpressure. The streamlined 4" turbine outlet pipe (not required with 325 hp systems), int ermediate pipe(s) and 3-1/2" tailpipes are formed of stainless, heavy-wall tubing with constant-di ameter bends to maximize airflow and lower exhaust gas temps. The dual tailpipes have 52% more flo w area than a single 4" tailpipe. Banks’ polished-stainless Monster muffler features a straight-th rough 4"-diameter flow-path with an exclusive expansion chamber to dissipate the annoying mid-rang e exhaust drone that accompanies most straight-through mufflers. The muffler utilizes spun ceramic , very-high-temperature packing, flows up to 129% better than stock, and delivers the signature Mo nster sound in stereo. Now for the cool part: A non-stock item. This is a SPECIAL ORDER!