I spoke with a representative from Vortech engineering about exhaust sizes with my current setup and he told me the bigger the better. I suppose this is for the most part true, but I am looking for an exhasust no bigger than 3".

I currently have the Gibson shorty headers on the 5.4L and the factory exhaust with a SIDO Flowmaster 40series dumped. I want to get more power out of my truck and feel an exhaust will certainly help. I was curious if removing the factory Y-pipe and substituting an X or H pipe will give any performance gains. I know I cannot touch the cats, so the only modification would be from the Y-pipe back.

Is the factory diameter from the manifold to the Y-pipe 2.5" I can't remember right now. Any help is appreciated, thanks.

 

I would cut the y out alltogether and go into a di/so or di/do muffler of your choice. Whether its 2 1/2" di and 3" so or 3" di and 3" so or whatever probably be hard to find 3" di just dont think thats very common, but really isnt going to matter that much.