Did the garage do proper leak off and fuel pressure tests or just a diagnostic scan on the ECU?
Sounds like the Focus TDCI I recently worked on, with the above symptoms. It needed 3 injectors.
Customer didn't want to spend £1100 so car was towed away.
I have been working on a Focus TDCI today with Delphi system, it has severe lack of power/smoking/knocking on accel. No DTCs to give me a clue, road tested & datalogged FRP vs FRP_DSD and difference is up to 80-90bar difference on accel when it's faulting. So carried out above tests and have found 3 injectors out of spec.
During 5 sec crank the injectors in cyl 3+4 had 15cm on fuel in them, vs about 5cm in cyl 1 and 9cm in cyl 2.
Results from 1 min and 4 min leak off test at idle confirmed that the injectors in cyl 2+3+4 are leaking off excess fuel, thus losing fuel pressure on accel.
LOTS of info about Delphi TDCI in this thread...
https://passionford.com/forum/ford-m...lp-please.html