Vortex is alright. There's probably more info there for you MKIV guys than us B5 guys though. Since I have a Passat, I usually hang out at Clubb5.com or Audiworld since the A4 is pretty much mechanically identical to the B5.
The B5 Forum on Vortex suffers a kind of 'Jeeps Unlimited' syndrome if you know what I mean. Sometimes the info there is kind of questionable.
Good luck with the Neuspeed Chip. They've been doing chips for a long time now. You getting the VBL 1.1 bar chip?