I have a problem with Peugeot Boxer 350 2.2 HDi. starts and runs fine but intermittently loses power and then won't start for a while. While driving along the engine management light comes on then immediately the engine cuts out. Seems to happen more frequently on slight inclines and has not happened on short journeys when speed is under 40. Had the RAC out once who diagnosed fuel pump - garage did diagnostic test and found no faults but since then it has happened maybe four times in a month (200+ miles) Any ideas?