Error Code P1556

[j0nesy]

just had my galaxy tdi 1.9 115ps scaned and was told it has error p1556 = turbo pressure control below minimal level intermitant

does any1 no what makes this error tried the maf and its not that

heres whats happening no power until 2000 rpm then loads on moterway slight incline and i have to gear down to 4th to keep the car moveing and useing a fair bit of juice aswell

[insider]

Perhaps the variable vane mechanism is stuck preventing the turbo reaching the required boost pressure? There are posts on here somewhere relating to how to unstick it.