Slight loss of power - any suggestions?

Currently experiencing a slight loss of power in me landy (300tdi d90). I can pull away and bring the revs up, and hear the turbo kick in (faintly, over the usual noise, of course), but just before it's time to change gear, the power dips.

It's not too bad driving locally, but when I want to get it up to motorway speed it maxes out at around 55. Until recently I could easily get 70.

I first noticed it when it snowed, so just put it down to cold and viscous diesel. But we've had a couple of warmer days since then and the problem persists.

Usually I'd think turbo hose, but hearing and feeling the turbo kick in for while before the power loss kinda rules that out. Any ideas anyone?

Check All the piping from the turbo make ure its not fallen apart In side or split on any including the pipe from the actuator and sensing pipe to the pump,

If you floor it at 55 does it kick out black smoke? If not when did it last have a Fuel filter?

Will do.

Haven't noticed any black smoke, although its me that's driving, so if it was just a little bit I probably wouldn't see it.

Fuel filter, darn. I didn't change that at last service. Did everything else but I think the new fuel filter is still in the garage.

This was happening to me, changed the fuel filter and it sorted it straight away