Appears to be a simple potentiometer
http://en.wikipedia.org/wiki/Potentiometer
This probably gets hooked up to the MAF sensor input to make the ECU lean out the mixture. It's a dangerous thing to lean out the fuel mixture across the rev and load range in general and without looking at the exhaust byproducts, you have no idea how lean it's getting, which can be bad for the life of the engine.
There's no quick and cheap solution to increased power in most cars and especially not with these Porsches. The only reasonably safe engine operational enhancements are done to the ECU (or by replacing the ECU with a tunable one) and are done while monitoring the engine's performance, timing, and mixture. A competent tuner may be able to eke out a little extra from an engine by being less conservative than Porsche was.
But this thing maybe worse than worthless, it may be dangerous.