Just to let you guys know, in case you don't know already, the stock exhaust is already as loud as an aftermarket performance muffler. I really doubt changing the muffler will provide any horsepower improvement, it would probably just make the Jeep a little bit louder.
For performance you would have to replace ideally the headers, or more easily you could just swap out some of the catalytic converters with high-flow versions, or even just remove them. If you remove them, then you have to deal with the oxygen sensors so that you don't throw malfunction codes (plus legality issues depending on your area).
My plan is to install "cut outs" controlled by an electric motor, for the dual exhaust system this mod will cost around $600. From the driver's seat you just flip a switch and 5 seconds later you have open headers just like a race car. I can't wait to hear the natural sound of the 6.1
This is basically what it would look like:
Exhaust
Linear Mode
