x pipes, makes chambered mufflers raspy, you can basically go two routes, you can change to a glasspack style muffler- LM2, magnapacks, and be REALLY loud or swap out your midpipe for an H or prochamber, the H will be less raspy but still have a pretty noticable drone, and the prochamber will deepen it out and have almost no drone...here is an example- O/R prochamber and mac flowpaths(chambered mufflers)
Mustang Exhaust video on Automotive