Audi A4 3.0 V6 TDI Quattro, after idling for a minute or so the car starts putting out blue smoke and the engine starts to sound & feel a bit rough as if it was off a cylinder. If I was caught up in heavy traffic, the smoke starts, when I get into the clear and I put the foot down the car puts out a large cloud of smoke but then clears after driving for a while. Any thoughts......

 

That type of smoke generally indicates valve seals and/or worn valve guides. The longer it idles, the thicker the smoke gets right? The rough running could be the oil diluting the fuel mixture or fouling the spark plug a bit. Do you also get blue on decel, especially if you downshift for engine braking? That would be another symptom of valve seals.

Rings would give you blue on accel and would get worse with heavier acceleration.
Good news is, the valve seals can be replaced without pulling the heads. If the guides are also worn, then of course they'd have to come off.