When driving my 2006 X-Type 2.2d it started to drop into limp mode when accelerating at low rpm. This could be reset by turning the engine off waiting briefly and then restarting. This problem became more and more frequent. After removing and cleaning the EGR and inlet manifold (filthy Job),which were not at all clogged, the problem still persisted so I booked it in for a diagnosis. They diagnosed that the moving vanes that control the effect of exhaust gases within the turbo and hence the speed and impact of the turbo were sticking, probably due to becoming coked up. They had tried to free the movement as a temporary measure but a replacement turbo was the official solution.
I took the car away and realising that the vane actuator arm was easily accessible just behind the engine cover, i decided to try to free the vane movement by unclipping the actuator arm (one circlip) from the electonic control unit and move the arm back and forth repeatedly and forceably through any claggy resistance, This seemed to reduce the number of incidents for the moment so I checked out what fuel additives there might be for cleaning turbo vanes. I found that Wynns produce a cleaner specifically aimed at the vanes and added that to the fuel.
I then drove the car in lower gears so that the car was revving over 2k rpm with occasional sessions of sustained 3.5k rpm to get the turbo and exhaust good and hot with lots of gas flow. This was interspersed (after things had cooled down!) with a further couple of sessions of actuator arm back-and-forth activity. After about 250 miles the problem had gone away totally but for good measure I have added another treatment to my next tankful and will still do some lower gear and high rev running from time to time.
So for under £40 and a bit of screwdriver and arm activity, I seem to have avoided a bill for £1-2K! to replace an otherwise quiet and undamaged turbo. In hindsight I could have also saved the £200 diagnosis cost by first disconnecting the actuator arm and manually checking out how freely it (and hence the vanes) moved through its full range of movement! Ahh the wonder of hindsight!
Hope this is useful to someone.