You have an internal air leak in the pickup system. Very common problem with the old Milodon dual external setup. It is less common problem with an internal pickup but can still happen.
It's the new Milodon oil pump and cover setup.
If it has an external line then that is usually the problem. If it is all internal then you probably have an issue with the pickup tube. Maybe a small crack in the tube or the block is cracked in the threads or something like that. Internal problems are rare but problems with the external lines are very, very common. I stopped using the external line systems because they were such a hassle.
