6n engine problem

[gaz2000]

had this issue for a while now,and its doing my head in

basically when im driving and come off the accelerator the engine doesnt de-accelerate properly? it kind of holds every second as its coming down,like its still briefly getting fuel or something?it does it untill i get down untill around 2k revs and its quite violent and very annoying,vagcom shows no faults and no sign of hg failure or anything else...

it does it in all gears,but the car idles fine and accelerates ok,any ideas?