aFe Exhaust Downpipe BackaFe Exhaust Downpipe Back If you are looking for a highly engineered down pipe look no further than the aFe Power Mach Force XP Down Pipe. Down pipe is 100 percent TIG welded and uses a stepped design that increases exhaust velocity and eliminates low pressure drops which helps to scavange the exhaust for increased intake charge and more power. Race proven strength and durability. Designed using a resonance chamber to help reduce the in cab resonance