Cheapest is to just remove the resonators at a muffler shop. I had that on my first exhaust on my 2011 GT
, with some Magnaflow mufflers too, by the previous owner. Sounded very good. Obviously a good over axle setup can flow more, due to larger diameter pipe (3" vs. 2.75") however some people have clearance issues with the panhard bar brace...which is why a few manufactures now offer spacer bushings to drop that brace down another half inch for the additional clearance. It can be worse on lowered applications.