My dad has a 05 Mondeo zetec 2.0 TDci 160k. Had issues with power delivery recently. When in the turbo range, if the accelerator pedal is depressed quickly (i.e. to give rapid acceleration) the revs shoot up to the limit but no power seems to be transferred to the drive. Keeping the accelerator where it is results in the revs dropping and then the drive picks back up again. I don't think it is the clutch as starting off in first is fine, it is just when the turbo kicks in. It sort of feels like a slower version of what happens with the traction control in my titanium x when driving in the snow. Any ideas?

it does sound like clutch slip, the lower gears will not show the problem because the gear ratio makes it easy for the clutch to grab,but in higer gears there is more torque going through the clutch so the slip becomes more aggresive.

i agree, if the tacho goes up but the speedo doesnt it has to be clutch