I have a 2006 BMW Z4 3.0si with 94 k miles on it. I did not buy the car new, so I have no service history. Recently, there is the odor of oil fumes in the cabin. From other posts, I have almost come to the conclusion that the oil separator valve is in need of replacement. When I remove the oil filler cap there is a vacuum sound. I have a good set of tools and moderate mechanical skills. I would like to know from those of you who have "shade tree" experiencing in changing this valve on a car like mine how difficult a job it is. When you did change the valve did you also change the related hoses, etc? I would also welcome any other constructive comments anyone wants to make. Thank you for reading this post.