Oil leak, no parts diagrams, please help

[NathanMartin]

Hi, I'm new here and have a problem which I can't seem to find any parts diagrams for. I bought my car (Insignia Facelift 2015 2.0 cdti A20DTE) used and since then it has been misting oil around the oil filler cap. This issue hasn't affected the car in any way but has been niggling in the back of my mind since I found the issue. I have, today took part of the engine apart to see where the leak was coming from, knowing already that it definitely is not the filler cap itself. It turns out that it is a seal on a component in front of the filler cap assembly which has degraded allowing oil to get past. This component does indeed have a part number sticker on it (under the intake bracket leading to the throttle valve) however this was also misted with oil and grime and when I tried to clean the dirt off the sticker, the printing came off along with everything else. this has left me at a loss as I cannot seem to find a parts diagram which indicates this specific part, nor is there a part number stamped onto the component (of course there isn't that would make sense and make life easy). my question to you guys is, would you possibly know the name of this component/part or have access to different parts diagrams which indicates this part? I have attached an image of the part with the cover plate removed, looking at the car from the nearside the front of the car being the left side of the image. I really hope someone on here can help, I feel like I'm going grey from searching for the part now.

[Vauxhall Owners Club]

It looks like the Exhauster which is an engine driven vacuum pump for the brake servo (fitted to diesel engines only)