Kirk:
If you want more horsepower, you're not going to own a Boxster to begin with.
Not to mention tuning Japanese vs European cars are totally different. You will definitely not see the same hp gain on a european turbo (say 1.8T off a VW/Audi) than japanese turbo (MKIV Supra or Mitsu EVO).
Let's see any european cars, including VW, Audi, BMW or Benz do this.
http://www.youtube.com/watch?v=OFB1S4T6B98