Well, I'm running an EEC Tuner and will soon be running a J3 Port adapter in the SVO...both of which allow me to change pretty much anything I could ever dream of (and alot of stuff I would never even think of). Both of these are under 300 bux.
If you want a standalone system (what the SDS, FAST, etc. are called) then I believe the cheapest is the Holley Commander 950 and then the SDS. Pretty much any of them will work with a 2.3T if you know what you are doing (FAST, Accel, Holley, SDS, Haltech, etc.)