It's a never ending quest to have the most, a little more than your buddies or at least a little more than you have now, regardless of the bike. 

Customers with a Kawasaki ZX12R will call us up and ask how they can add more Hp. We say, "you already have the most". Customers will always reply "Yeah, but it's still not enough." 

...STAINTUNE exhausts are engineered and tested to improve the overall efficiency of a stock configured motorcycle. While our systems are not designed purely for racing conditions, they will enhance the performance of your bike, with an average being one or two more horsepower on almost all applications. Some bikes might get more, but you won't lose horsepower. This is done with no other modification of a chip or rejetting needed.

Typically, bikes come from the factory already needing some sort of change, even without adding an exhaust system. You won't gain heaps of horsepower by adding just an exhaust, but you also will not lose horse power because you failed to also change your air cleaner, reconfigure the jetting or install a new chip and advance the timing as is standard practice on many of full-on sports exhaust systems. Staintune high-flow exhaust systems help produce more efficient power along with snappier throttle response and smoother torque curves within the frequently used mid-range power, all without excessive noise, and many riders report better fuel economy.