I originaly went with 2 1/4" cat back with a MagnaFlow muffler and had a noticeable power increase. I ripped a hole in the MagnaFlow at Moab and replaced it with a Summit turbo, power increase gone. I think the MagnaFlow made the diferance, not the bigger exhaust. I went to 2 1/2" because I am planning a turbo install down the road. I have a 2 1/2" MagnaFlow cat going into a round MagnaFlow muffler in front of an ovel MagnaFlow. My power is good but it is very loud but I am banking on the turbo to quiet it down. With our little 4 poppers I think a good flowing muffler makes a bigger diferance the pipe size over stock. I like MagnaFlows for thier ability to free up power but on a FE3 motor they are loud.

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.