This thread seems to perpetuate the myth that an open pipe or one with less internal obstructions merely needs fueling changes to outperform the stock design. It is not nearly as simple as that and even reputable companies only sell replacement systems that are dyno proven to produce the same power as stock. They may claim slightly more torque in parts of the rev range but can almost never produce significantly more top end power.
The standard exhaust is designed to have an effective length which is matched to cam timing and other engine parameters and it operates in a resonant way which is completely broken if you remove its internals or replace it with an open pipe.
The exhaust design of this bike is one of its best features for exactly the reasons described above and in my opinion even the factory approved alternative is no improvement except for a better sound.
