This is more of a how not to do it.
Having swapped an auto engine over into my glacier blue manual car there was a hole in the side of the head where the vacuum pump used to be (or dizzy on older cars).
The part number is 91 35 211 for reference and I bought one here:
https://www.saabits.com/all/saab-900-9000-9-3-9-5-cam-cover-plugHaving sourced the bung and looking at the design I concluded that the lip on the outside edge sat in a groove. This was a mistake.
So, next task was to take off the cam cover to get access to the inside and slide it in from there. I was faced with a false cam bearing, secured in place with two security T40 torx bolts. They were very tight, too tight for a 1/4" drive ratchet, at which point I looked in WIS for some instructions, and after finding nothing there went searching on the internet.
After a close look inside the false cam bearing cap I saw there was no groove and it was confirmed that they are just a push in item. which is what I did, using an 18mm socket, see photo.
After that it was a matter of cleaning all the old sealant off the rubber / silicone gasket, putting on some sealant of my own, very thinly and making sure nothing can move to the engine internals, and reassembling. The cover is on hand tight, I'll torque it up tomorrow and that I think is the final job on the job swap.
The head itself looks very clean, though there was a bit of mayonnaise on the rear timing chain gear. Too much time spent on cold startups I assume.