Why do you "need" to make it faster, is it for you or for racing?
If your drag racing the classic answer is that this is the wrong car for that. If your racing on a track improving your driving could help without spending any money (This is just an idea, I have never seen you drive, don't take offense).
Now there are only a few ways to get more HP out of a Boxster, and they can cost a lot. Desnorkling is a proven 5HP, then you can get a super charger I believe there about 5-7K, then new headers and exhaust might help. So since your looking at about $10k right there, your better off to just drop a new engine in for about the same price but you'll get more HP.
There is no easy way to add a lot of HP to these cars.
