+1 just get a ECU flash from Steve.
Changing the muffler does nothing for performance, it is just cosmetic or to create unnecessary noise (or maybe to save a little weight). Changing the entire exhaust system is expensive and really doesn't do lot for performance either, it will shift some of the torque from lower RPM to higher RPM (which is really no advantage for the vast majority of use cases). The C14 doesn't have an overly restrictive exhaust system like old bikes of the past. Most of its "restriction" is in the stock maps inside the ECU....
Reflashing the ECU, on the other hand, is huge. It gives more power overall (including peak), gets rid of the "lackluster zone" in the middle RPM, and (if you choose) also tames the hyper-throttle. And with all that, my MPG actually went *up* a little with normal use- a clear indications of a good/effective tune. The ECU reflash should easily surpass the results of a PC, overall, and is easy and "stock." As far as I know, everyone who has done it has been very happy.