Email my buddy Stealth TDI. He has a 1998 model with around 200,000 I think. He has been using Amsoil in it since 2000. He also had a by-pass and other goodies. He now races it in SCCA, but he is a wealth of information.
http://www.stealthtdi.com/
http://www.stealthtdi.com/
quote:
Although I'm a bit of a leadfoot, my lifetime average economy over 175,000-miles is over 43-mpg. I can get over 50-mpg simply by DRIVING THE SPEED LIMIT. My best tank without AC is 802-miles on 14.58-gallons, yielding 55-mpg.