I believe you have a leaky head gasket.  These things happen even on VW
factory rebuilds.  Take it back to the place that installed it and try to get
them to check it out (sniff the coolant tank with an emissions machine to see
if there are combustion gasses in there) and then if there is a problem get
it fixed under warranty while you can.  That is why you paid the premium
money for from the dealer.

Hope this helps,
Ken Wilford
Van-Again
John 3:16
http://www.vanagain.com
Office: (856)-765-1583
Fax: (856)-327-2242