I don\'t have a Jetta ,so I can\'t help much, but I have done a few mods to my car with more to come.
Last spring I had gears installed and I put a chip in to boost the timing on the car. I think the timing gave the seat of the pants kick I was looking for, plus the gears helped out a lot as well. Pulleys are going on this spring.
I wish I could go outside and do some work on my car now.
Ace