I think a lot could be in the muffler. When I tore a hole in my first MagnaFlow I replaced it with a Summit Turbo and lost power. The MagnaFlow has a way of building power. They do make noise though. I have a few hills on my way to work and judged my power lose and gains by when and how often I have to shift down. Seat of the pants I can't feel much either.

Dennis

95 Sportage, gone but not forgotten.
98 Jeep TJ, 4" Zone springs with RC Long arms, Ford 8.8", 4.56 gears & Detroit locker rear, D30, 4.56 & Detroit Trutrack front.