Can anyone tell me what this connection is that’s not even plugged in anywhere ?

 

Hmm. I can't quite tell but I do know that the little interior air sensor (it has a little fan and sucks air in to measure for the climate control system)... has a foam covering over the connection like that from the factory. It could be that, as it is definitely down around the fusebox. If you look to the left of the steering wheel by the mirror switch, there is a little piece of plastic with slats in it. Behind that is the interior air sensor, that may be it? Pretty easy to find with the fusebox cover dropped down as you have it.