I would stick with 2.25" for a near stock SVT, the 2.5" will kill some flow velocity at anytihng but redline. If you run a good 2.25" setup, you should pick up some tq along w/ the hp. and honestly, when I did mine (I went w/ 2.5" cuz the guy did it for me for free :D) I don't think I got any tq gains, though I did pick up a bit of hp (butt-o-meter)
as an aside, when I got the SHO-shop Y-pipe later I did notice a decent gain in tq
