I have been having some idle problems with my TDCI for a few weeks now, it was there when i bought the car but no matter what i have done it has not gone away but has got worse at cold and sometimes alot better with some heat in the engine but not always. I have cleaned and blanked off the EGR valve aswell as the manifold and every boost pipe and tightened them all down, the car has just had a full service, every sensor that i could reach has been removed and cleaned aswell as there contacts but with no real improvement. At cold it chucks some unburnt fuel out and idles rough then i can drive 10 miles then stop and it is maybe only a little better but if i turn the car off for 10-15 minutes and return to it then it has a habit of idling without any issues at all.
The only small thing i have noticed is that the temp gauge drops a little if i am slowing down or i stop and the temp drops away very quickly if its left standing for 5-10 minutes.