Rattle from passenger side air vent

[EVO575]

Since Ive had my car-1998C2-its had an annoying rattle from what seems like the passenger side air vent.My friends 99 car has the same.Question-is this a common rattle with an obvious cause or is it a case of investigation?-lastly,the vent has two visible torx screws holding it on,is there anything else holding it before I start screwing my car apart?!!