black smoke and hiccups

[jedro750]

My 2.0tdI passat stutters between 1500 and 1800 rpm, it then clears then you accelerate up to 2500 rpm then the acceleration comes in really hard (wheel spins in first ) and you can see the black smoke out of the rear mirror, I've replaced the MAf and the engine runs smooth and fast after that sharp kick at 2500 rpm, averaging 44 mpg, it's had a recent new turbo, vacuum pipes and actuator, no faults show up on a VAG_COM . I've a friend who has a vcds but he and I don't know how to interpretate it , so I'd rather try someone else, ---Any Ideas please ???, Jedro.