I found this site by a google search. 1999 Passat (V6) Hard to start after gassing up! that is the title of the ppost on this forum from 9-3-08. I cannot find it on here now so I am posting for myself it is 5-28-09 for anyone in future that finds it.

That is the problem. When I refuel the car does not want to stay running unless I keep the motor racing. I haven't been able to get away from the pump w/o less than 3 restarts yet. What is this problem? I have read some stuff about it being a valve in the EVAP system.
If someone knows about this and knows what to do I'd really appreciate it.

Edit after some research,
I've been doing some research and I have decided to change the N80 purge valve as it seems this is a very common problem and that was the only solution that anyone who bothered to post their fix found. I had already changed the gas cap.

 

6-11-09
I installed a new purge valve and will let you know if it worked on next fillup. I still have half tank so it'll be a week or so.

 

6-15-09
I went for a long drive over the weekend I had the computer on it and all is well. So I filled up today and it started first time! I'm betting this is the fix for the restart after fillup problem.