A lot of people talk about the DynoJet Power Commander, but not much talk about how the Power Commander actually works. The thing is no matter how tight a manufacturer's testing procedures are, there will always be minute differences in tolerances when building an engine, making every motorcycle individual.
The problem is that a manufacturer can't individually set up every single motorcycle it makes, so the standard ECU contains a fuel map that is a compromise. Your motorcycle is designed to work anywhere in the world irrespective of the height above sea level, quality of fuel, density of air, humidity, etc...
Which is all very well and good, but are you likely to take your Thai Kawasaki ER6N to the arctic-circle an run it on crap unleaded fuel you bought somewhere in Pakistan? Probably not, which is where a DynoJet Power Commander comes in.
A DynoJet Power Commander, or any other similar device, works by bypassing to motorcycle's ECU and creating its own fueling map. Rather than rely on what the motorcycle manufacturer has decided, with a Power Commander, you, or more likely a skilled operator, can tweak your motorcycle's fueling to deliver exactly the correct amount of fuel to the engine.
Rather than rely on an average, your motorcycle's fueling is tailored to suit it. It's a bit like buying a made-to-measure race-suit rather than an off-the-rack one. Because this is simply optimizing your motorcycle's fuel, huge gains in power are likely, but this isn't really what a DynoJet Power Commander is all about.
As well as the 5 percent or more gain in power, the motorcycle will feel sharper and more responsive because it's running closer to its optimum level. The benefits of this tailored fuel map are apparent even with a standard exhaust fitted, but to gain the extra full advantage, you need to set your motorcycle up with a race exhaust system fitted.