According to the mondeo owners club they are saying it's the EGR valve, had a quick google and it's come up with this post...
I have a TDCi but suffer from the same syptoms.
The power delivery from when you accelerate is accompanied but a jolt that can be felt through the car and this seems to make everything else feel loose (Steering, Engine and Gearbox).
You speak of throttle position, i seem to get power by depressing the pedal very slighty. If i depress it fully i get nothing, but if i lift it from the floor bit by bit the power seems to come back.
Ive also changed oil cooler stat as temp guage was slow in moving but has made no difference, the needle only seems to move if im apply power and slumps once off power and in traffic.
Is it a case of tuning the engine (injector spray patterns, timing etc)
The thing is, if i switch the car off and then back on again i get the full 130 power (its amazing) for about a mile. 1st 2nd 3rd pulling to red line, i get to 4th (3000rpm) then its like a limiter cuts in and im back to climbing the revs like a snail again."
Might aswell try disconnecting it. You will lose power but if it stops the problem you know it is this.