Wondering what the little box is above the rear seats on the roof. I thought it was a thing for like rear ac, but I took it off and nothing was there...

Just wondering what it was

 

If you get the factory alarm it is where the motion sensor goes. No alarm = nothing there.

 

So that filter looking think is just ascetics I am guessing

 

It probably keeps dust from effecting the motion sensor (if installed)
I've had mine out a few times. There's a wire up there I'd like to utilize. I just need to figure out when it has power and if it would hose anything up if I tapped into it.