[jdraupp]

The first upgrade I'd make is to add an s between box and ter.

Now that that joke is out of the way, welcome. If you do a quick search on this forum you'll find many opinions on getting the most out of this car. One thing you'll notice about Porsches is unlike american muscle they've really done most of the potential maximizing. There are not many easy strap on performance mods that add much because the thing was engineered to make the most of what it has.

For the 2.5 there is a tpc supercharger available that adds a bit of hp as well as adding an under drive pulley can add about 7 horsepower. Desnorkling doesn't add anything but a bit of growl from the exhaust some say it does take away some hp but it's pretty negligible. There are threads on both of these including a guy who put the SC on his 98.

Obviously if you're handy and you're looking for a boost, you can swap your 2.5 out for a bigger carrera engine, or trade your 98 in for an S model. Assuming those are out of your price range though.

As far as air filters, general consensus is stay away from k and n oiled filters. The paper factory filter is just fine.

The best way to add hp is to go to driver education events and track days. That car will never be a straight line car, but what makes it so special is how it handles in the corners. If you learn how to unlock it's potential you won't think it's so underpowered. Trust me when I say that this car can handle much more than all but the highest qualified Porsche factory driver can throw at it. Make sure your tires and suspension are good and learn how to drive it like you stole it.