[EPIQTodd]

It is hard to get too much gain in hp from naturally aspirated engines, typically - those are more designed (and FAR more effective) on forced air engines, where the boost can be easily controlled. Still, it is the best bang for your buck, but there are still others out there who swear that it does nothing. Same with cold air intake. Several Porsche techs have told me that what is in the Boxster already IS a cold air intake, and that aftermarket intakes actually are hotter than the stock - all depends on whom you speak to.

Cat bypass pipes definitely increase hp, but not a terribly large amount, because you are improving air flow directly. New mufflers can, but if they do, it's SO slight.

You might feel it is slow in a straight line, but take it on the track and see if you can drive even 50% of its potential - that might put the desire to upgrade power down the toilet. Plus you get hooked on driving the car for real!