I can't afford all in one go. £150 each is the current rate. So £600 and that's if you can do it yourself. As I can so guess I'm lucky. I am doing one at a time. I did the first one. It cured it for 2 months. But it's started again so I can just about scrape enough together for two more this week. But as previous guy says. Get it fault code checked. I get "P1211 injector control pressure higher/lower than desired(engine running)
P0251 INJECTION PUMP FUEL METERING CONTROL A. " pretty generic I'm told. But I am certain that's your trouble. Mines only done 96k. Keep getting told it's supermarket diesel and you must only use a genuine ford or Bosch fuel filter. Filter down to 2 microns. Non gen lets a bus through. Good luck pal. Oh get a leak off test done too. That'll tell you for sure.