Description Mod Mafia FASS Fuel System is designed for 2001-2010 Duramax Engines.  We have made a specific weld-in mount that puts the FASS System in the perfect spot, above the bottom of the frame rail – This is a must for any Dmax Swap.  Its helps protect all the expensive fuel system parts downstream, plus makes more power. – The system makes it easy to plumb in the truck. – The system is also positioned so the filters can be changed easily.