[Vwdiesel] '01 Golf TDi - small gnome in the engine with a hammer?

[Rolf Pechukas]

very recent development, noticed after latest oil change (Mobil 1, Extended)
at idle, running rough/stumble-y (not about to stall, but not the normal swiss-watch ticking I'm used to, either)
is this a typical sign of something? anything I should be looking for?
late on my timing belt service (204k on the car, been 70k+ since I did the belt)
thanks,
Rolf in MA