I have a continuing problem with my van. When driving the engine will cut out and very low oil pressure will come up on dash. I have changed oil pressure sensor,fuel filter,oil filter, turbo. I have taken off oil sump and cleaned the metal gaus.it looked clean to start with but cleaned it anyway. Took it for a spin and it,s still giving a few cough,s. Does anyone have any advice on what might be the problem?