I have a focus C-max 04 reg 2ltr TDCI and have the same problem
you can clean the EGR valve which is poss dirty, when the valve sticks it looses power like there is no turbo.
when it goes dead stick its called limp mode.
usually to protect the engine, this is poss a condition of the egr valve.
I have ordered a haynes manual for my car and going to try some cleaning of said valve.
if you have it tested on a diagnostic machine it will poss tell you its the sensor or solinoid which on my car is the same part (which is what I have changed to no difference).
you can also aparently use a blanking plate to isolate the egr valve so you dont get the problem this stops some black smoke when you kick down the accelorater
and gives you some extra power too.
Lee Hooley
May 2012