newbie question:tdi w/143km rough running at start

Hi, cold morning in london ontario with full tank of fuel tdi started ok, but pulsed few seconds later.
new filter, plus 2 tanks of fuel later still starting this way. (with first start of day) Starts OK then 15 seconds
later, rough running, which continues for first 2 km or so. On advise from VW have added standyne to
current tank. Is my problem still fuel? Or injectors/engine control/air. Don't know where to look.

thanks.

I think I would look at the clear fuel line right after I started it to see if excessive air bubbles develop. If so, I would suspect an air leak in the fuel system.

I have observed the fuel line, but did not notice any sign of much air present. If you had a line leak
would you not have this problem most of the time for startup, and not just when starting cold?