There seems to be a lot of misinformation online... I currently have a stock 2.25" catted mustang h-pipe on my vehicle. My 351w should be pushing 375-400hp at the crank (trying to be conservative). How restrictive is my h-pipe compared to a 2.5 catted pipe? I do feel its lacking in the upper top end (above 5000rpm), but the cam should still have plenty of power up that high, so that's why i'm wondering if the pipe is holding me back.