I want to run a 2.5" inlet/2.25" dual outlet MagnaFlow muffler on my 4.6L 2002 F-150. Do I need a X pipe, Y pipe, or H pipe? If so which one and what difference do they make? Will this retain my backpressure or will I still see a loss? Thanks.

 

Your truck has a V engine (V6 or V8) meaning it has two banks of cylinders. That means two sets of exhaust headers, 2 cats per exhaust side. The F-150's have a Y-pipe taking two 2.5" pipes and combining the two sides of the engine's exhaust into one 2.5" pipe before the muffler. When people discuss X,H, and Y-pipes, they replace the OEM y-pipe with their choice of H, X, or (better designed) Y pipes. If you replace the muffler remaining pipe (like most people do), you don't need to do anything else. If you want a SI muffer, don't get an X or H-pipe. You could replace your OEM y-pipe with a nice mandrel bent one and a 90 degree elbow.