If you are supercharging then talk to VF engineering, I was there in Dec and was really impressed with their shop and expertese. The Jetta has had the stage 1 setup on it now for about 35-40K miles with complete reliability.
Just drove the car to Napier at easter and its realy given me a new respect for it with the way it runs on the open road, I mean 6th gear up hills and passing just awesome!
It just pulls like mad in every gear and just seems to keep on going, the rate of accelleration doesn't realy let up until 120mph so it will be very interesting to see what double this HP does.