This has been a bit of a thorn in my side.
It was giving an underboost code at the slightest hint of a hill and going into limp. I bypassed the vacuum on the boost actuator and was able to get an overboost, so happy days replace N75 and it is all fixed... or so I thought.
Now it gives underboost after 30 minutes or so on a bypass and only at or near to 65 mph without any real load change.
The only thing I could think that may alter here would be EGR so I have given it a good clean up and I think it is now sorted ( I will confirm in a day or so ) but I also found that the throttle valve electric plug was full of oil.

Has anyone seen this before ? I cant see anywhere that it could have got in from. I was suspecting that it may have come up the wiring, but there doesnt appear to be any oil in other components.
Customer did report that on occasion the instrument cluster reports that the oil level is low even though it isnt