Banks Power 03-04 Dodge 5.9L Muffler Kit - 4in X 4in S/SMonster Exhaust Benefits. Replacing the restrictive stock muffler with Banks' free flowing Monster muffler makes a huge difference in airflow, sound and performance. The Banks muffler has a large inlet and outlet. And in between, the exhaust flows straight through, instead of torturously winding its way back and forth inside hairpin chambers and building up back pressure. And only Banks Monster muffler has an expansion chamber to alleviate the nasty