[ronster]

If you do a search here there is a lot of information on what you seek. The short answer is there are a lot of claims but reality is there is not a lot of hp gains to be had from the 2.5L unless you turbo it. I've made several mods to mine including EVOM CAI, Fabspeed headers and Dansk sport exhaust and only because I happened to be at the right place and time to get that equipment at a screamin' deal. To really find out exactly what you're gaining you would need to have your car on a dyno pre and post and that gets expensive. What I was after was more torque to the ground for AX and overall I believe I've improved torque, by exactly how much I couldn't tell you but my '99 Tip seems to run better, have more pick up and sounds like a Porsche should. Good luck in your search, there are a lot of good low mileage early Boxsters out there at a good price. I've never stopped loving driving my '99 in the three years I've owned it and my recommendation, before you do any mods, is to learn to drive the car by participating in AX and DE events. You'll find that although the car may be slower than the 911's it has capabilities that go far beyond your skills to tap into until you learn how to drive it and once you do it's handling characteristics can make up for less hp. Have fun!