Same as a chip tune. A Tuner will write you a new tune with what ever performance changes you may want as well as an EGR delete, rev limiter rpm change etc. and the old tune is remove from the ECU and the re-written tune is flashed to the ECU with a chip loader.
The reason VCDS can't do it, is because VCDS doesn't write anything to the ECU. It just allows you to make different selection of things that are already written to the ECU.
If you are going to do a tune, learn as much as you can about how chip tunes work. Call up RocketChip, Malones, GDE etc.
After going to the GDE website, I would suspect what they offer, may not be suitable for our TDI's. But IDK.
Last edited by Ol'Rattler; 03-13-2012 at 09:57 PM.