No need for a new turbo, its usually all done to sticking turbo vanes, there are some chemicals available to dissolve the built up soot, and a few garages offer this service.
But before doing that, if you have half a day spare at the weekend and have use of a decent hill, its worth doing a good old Italian tune up.Warm the engine up first and then repeatedly load the engine up in Forth on a good hill. of course the likely hood is you are going to go into limp home mode but persist by repeatedly loading the engine up. Each time it goes into limp mode pull over switch off then switch back on.
A lot of the time by persisting this actually works, if it does don't forget in future to let your diesel rev past the 3250 rpm mark a few time more regular than maybe you would do as normal, to
help the turbo vanes to keep from getting really badly sooted up again.