T3 Golf GTI, Digifant conversion.. Oil Pressure problem

[Stefvan]

Hoping someone has been down this road.. got a 1.8 GTI PB code Digifant engine from a Golf Mark 2 in my new bus. It has apparently been running fine in there for a few years, but apparently none of the sensors were attached, as I found the wires coiled up in the corner of the engine bay. Now they are all connected the oil pressure buzzer comes on at odd times. The engine is up to temperature and the van is either slowing down, going up a hill or going round a corner. My instincts think its something to do with the oil pickup pipe, its the wrong one, or its partially blocked. Unfortunately due to the way the exhaust has been welded to the sump, (the bolt sockets in the sump probably stripped or mullered) and a bracket made up to support the power steering pump, it's an expensive pig of a job to get the sump off to take a look. Do I bite the bullet ? Sensor cable checked, I have ordered an oil pressure tester to double check the normal pressure. The oil pump was renewed when the conversion was done 6 years ago and the van has only done 3K miles since

Stefvan