What would be the most effective way to increase power on my bike?

Not trying to sound smart, but if there was any cheap horsepower in your bike just waiting to break free, don't you think Kawasaki would have already turned it loose? The problem is that your bike just isn't all that powerful. Compared to other 250s, at ultra high rpms it is more powerful than most, but that still isn't a lot of hp. The least expensive way to get more power would be to take the money you'd spend on modifications and put that toward a bigger bike.