If you want more HP then what you really want is a better HP to weight ratio. Less weight will improve the HP to weight ratio so what you really need to do is lose weight yourself. This will have a multitude of benefits for a number of people. Not only will you go faster, you will spend less money of food and spirits so you can spend more on your bike. It may also help your health, less joint stress and decreased possibility of cardiac problems and possibly even diabetes. For you guys that are already skinny then you are SOL and will just have to spend money on your bike to improve the HP to weight ratio.
bob