VW Vortex
VW Vortex forums are the best I have found for finding out any info about VWs. I know mk1s and mk2s pretty well, but beyond that my knowledge quickly slips on the newer models. With the Vortex make sure and supply details (tuning, mods, all that) it will help you get a good answer as quickly as possible.
Good luck, a slipping timing belt is not a good thing.