hi all, im new to this forum.

I have recently baught a 2005 A3 sport 2l tdi, think its been mapped

the car pulls very well but it is very erraric and lumpy on idle, it does it whilst cold and whilst warm.
it starts quite well (quickly off the key) when cold but when it warms up the engine cranks for a fiew seconds before starting.

the car runds well whilst going along, has plenty of power and pulls strong!

I have read so many possible thinks this could be but can anybody point me in the rite direction, where do I start?
im from south wales, Swansea/llanelli/Carmarthen area, should I get the car plugged in? can anybody recommend a good specialst and how much should a diagnostic cost roughly?

is this complaint common on here, the rough idling issue?

many thanks and apologies if ive posted in the wrong section?
thanks, mark