I am going to have new exhaust put on my mustang. I want to go with a single in dual out muffler (thrush welded muffler or equivalent). I was thinking of going with 2.5 from the manifold to the muffler and then 2.25 duals out of the muffler. I realize this is big now, but I want to add a few mods like a header, mild cam, and perhaps a 250 head and better induction. What size would be best considering my future mods. 2.5 or 2.25?