What is that for ???

Not sure to be honest - but as it says Intrusion I googled  Sens Assy Intrusion and it appears it’s part of the alarm system.

 

At a guess its the interior microwave sensor?

 

I could be very wrong though :-/

I agree.

 

Hm… but the place is weird. I saw some pictures of others NC and there was nothing in this place but I guess all of MK3 have alarm as a standard…

 

BTW: I removed all plastics - now it is reeeeeaaaalllly loud inside

On the lable - Fujitsu Ten Limited FTL 186.  Google search identifies it as “Automotive Security Field Disturbance Sensor”.  Does that help?