2.0 Diesel - poor, 'shuffling' idling

[TheBFJ]

Esteemed Members.....

 

Our 2.0Diesel estate was neglected before coming into our fold and had a few issues. Nearly all have now been sorted now but one remains - the car idles very poorly. Accelerates well, cruises well, economy is good etc etc BUT the idle is not right at all. When coming to a halt the idle returns to a steady 900 rpm or so for a couple of seconds, then the revs drop to about 750, it hunts around and makes sounds that I can only describe as 'shuffling' - which probably isn't a technical term. Never stalls but just not Jaguar-like. The air mass sensor has been replaced and I'm hoping someone will suggest something simple - like a air/vacuum leak or similar - but dreading any reply with the letters DMF in it. The letters EGR I could probably cope  with. Any hints welcomed. Also - I keep seeing references to blanking plates on the EGR. What are the pros and cons of this? Granted, I am ignorant, but surely it must affect SOMETHING adversely? And, if it doesn't, which would I need to get?! Ours is a late 2004 model.  Many thanks. Graham