I got my extra diff and gear box drain plugs ages ago but have been prioritizing other stuff. The reason for buying some extras is that my first try didn't go very well. The pice of sh** Biltema tap broke and made the drain plug useless.

I have been looking around for a proper 1/8-27 NPT tap here in the Oslo area. The only one I found was industrial strength and cost almost 900 NOK... Too much for a one time job.
A dude in the same garage as me told me the other day that the Biltema tap works as long as you use a lot of oil and rewind the tap completely for cleaning when the resistance suddenly increases.
His advice actually worked out great. It took ages to do but at the end both the 300F VDO sensors was securely fitted with Locktite:

The wiring from the dash logger is already in place. Just need to get some new oil before replacing the plugss which probably won't happen before end of March.