My fiesta 1.4 TDCI - 03 model 37K miles has become very slow upto 2000rpm then surges off, thereafter its performance is fine.
I have changed:
Fuel Filter
Airfilter
Checked for Vacum leaks in pipes
Accelerator pedal with sensor
Turbo !! on advice from Ford that an actuator had siezed
ERG Valve with associated Solenoid valve this seemed to make a difference but it has since slowed down now

I have disconnected the MAF and it runs much better with no lag under 2K but i could just be bypassing the Engine management system. I am fitting a new MAF tomorrow if this doesnt work i may try the lambda sensor but after then i have run out of ideas.

Has anyone had a simlar problem or any ideas ???