I have a Ford Focus 1.8 TDCI 52 reg it was remapped prior to our purchase.
The problem I now have is that the cam belt snapped, the engine was repaired with full engine head rebuild (with a refurbished part). Now when driving as soon as the engine gets hot ( temp half way) as you are driving the engine begins to hesitate/hold back/physically jump. If you accelerate hard it will recover only to start doing it again moments later.
We have had all fuel injectors tested and remounted and sealed, it doesn't throw out and codes on diag even when driving along with it doing it.