I have added very little to this car and I plan to add little else. There's really not that much to do anyway. Porsche already did all the easy high-performance stuff all the way down to the H4 headlights. It was, after all, just about the fastest thing on American highways in 1988. Still, a few tweaks here and there help keep it fun.

First thing I did was take it to Custom Sounds to install a top of the line alarm system with anti-carjacking features.
K&N air filter
I found a filthy K&N filter installed after I bought the car. After a cleaning it was fully servicable.
Dual-tone European air horns
This was a fun mod I performed after I discovered the factory Hellas were broken as a truck was wandering into my lane. They make me smile every time I tootle. Hee hee!
New floor mats
The originals were worn and horribly faded. I got these for xmas '96 while Automotion still had some with the Porsche crest on them.
Mirror covers
These "bra-lettes" or "ear muffs" are pretty stealthy (as in invisible). I have a few rock dings in the nose and hood, but the mirrors look awful. They are the only thing that really stick out from the smooth aerodynamics of the rest of the car so it's no small wonder. If the paint were any color other than black I might not be so hip to this plan.
Zero-toe alignment
This causes some tracking in ruts but the on-center steering is quick and responsive. It also wears the front tires a bit less.
Rear Muffler Bypass (RMB)
This simple pair of pipes replaces the rear muffler aft of the axle, leaving the twin primary mufflers just in front of the axle. It's a little noisy for long trips but it's a real thrill around town. This modifications removes almost twenty pounds behind the axle and sounds like a V8 should.
17" Porsche 928 GTS wheel replicas
These wheels look like those found on '94-'95 GTSs. They are one-piece cast wheels made by Mille Miglia and they look terrific even if they aren't terribly light weight.
Poly front sway bar bushings
Not much of a performance adder but they were cheap, greasable and reduced some suspension squeak. Not bad for $25.