I’ve had very similar problems to yourself with Focus 2.0 Tdci 2005.
Turns out that the eolys oil thats used as an adative hadnt been topped up during its 37k service and that meant a gradual blocking of the diesel particulate filter.
I went to Ford main dealer and sked why this hadnet happened ( I bought the car at 38K). They explained that the car must have been a fleet car and that fleet managers usually opt not to have it done.
I have two options.
1 – Pay £200 for oil top up/ ECU reset and DPF regen.
if that doesnt work Ford want £475 for a DPF and £200 to fit!!!!
2 – get the car a delete pipe and have the ECU remapped to null the DPF sensors and eolys oil sensors.
Problem with first is the expence.
Problem with second is that I’m not ceratin that it would pass an emissions test during MOT.
Total nightmare.
BTW – before everyone starts to blame Ford, most if not all diesel car manufaturers have used this DPF as a work round to Euro4 which was an emmisions rule introduced in 2005.
VW/Audi are by far the worst as a dpf for audi a4 is £1100 parts only!