Does anyone know what the diferance in performance is on a round muffler VS. an oval muffler would be? I am looking at getting the MagnaFlow SI/SO, just wonder on which style is the best for all around performance and sound.

 

Realistically, none. Shapes are predominently used to achieve a proper "fit" more than anything else. What you do want to look for is a straight through design. The minute you start changing the direction of air flow you create restriction. There are some engineering principles that can offset these, but if you look at your high end $ units from "Borla, Hooker, Magnaflow, etc", you will see something they all have in common.....a straight through design. In terms of sound, one persons love is anothers hatred....what I do when I go to a shop to have a set of pipes put on, even if I think I know what I want, there are too many variables in vehicle production & pipe production which can change things, so I have the guy cut off the pipes, hold a muffler up and listen to it at idle, highway rpm, and reving the engine inside and outside and to the side of the vehicle to see if that is the sound I want.