I would expect the cam sensor code (P0340) to be cause of cutting out completely, especially if it's an original 'black' coloured sensor. Modified sensors are grey and it's advisable to add 12v feed to sensor instead of 5v reference to give a more stable signal.

P0251 is set when fuel rail pressure actual is different from fuel pressure desired, it can be an IMV fault (inlet metering valve) but also can be fuel pump fault, or excess leak back from injectors reducing fuel pressure.

If you do a search on this forum for p0251 there are many threads with info about this code and possible remedies.