I would ask you for some clarifications.
Q1 – Is your car a 1983 300D Turbodiesel,
300SD,
300CDT, or
300TD Turbodiesel?

Again, I am not entirely sure of what you mean by “Airbox” so take a look at this engine external part’s blow-up diagram and see if you can spot the components you are speaking of:
http://www.performanceproducts4benz.com/Drawings.aspx?bmid=150
Sam