Vauxhall Astra fault code p2015 intake manifold control valve actuator internal performance too short low time.

I have noticed my fuel economy has got worse, I have oil in the intake manifold I also think am getting diesel in the engine oil. The car has no warning lights apart from the DPF warning light comes up if doing short journeys a lot and then when I take the car for a spin it goes out and will come back the next day. I have checked the EGR valve, which is fine. Checked and operated the intake manifold valve which works but it’s seems to me it’s randomly opening full and closing over when idling. It’s like the engine is hunting for something.