You shouldn't have to slip the clutch that much or not at all. Its a Volkswagon. Obviously this is the first one that you have owned. Even with a turbo you shouldn't have to rev to high. Ask anyone that has own more then just a mk4 and just a 1.8T. It doesn't drive like most turbo cars. Its german, and they like the low down tourqe and they don't like having to rev up for there power. So try lower RPM. You should be able to get a better launch. If you don't think so just ask Code-7, LostBoyScout, or Saly-D on the Vortex. Thay'll tell you the same thing.
Its hard to explane if you haven't owned a VW before. There different then that other cars (Japan, American).