I believe others have called it a stumble. I have not noticed it very much on mine but from what I've read in the section specifically for our Passats http://forums.tdiclub.com/forumdisplay.php?f=86 it is the reprogramming. The new program places an emphasis on warming the engine and exhaust system. To do this they restrict the exhaust flow to heat the other components faster. While this is being done performance is impacted. You should be good to drive, after a couple miles it should be warmed up enough so the program stops doing this.