328 HVAC intake filter in front grille

I am replacing the air duct hoses that run from the fans to the heater cores in my 328, and noticed there is a mesh filter over the HVAC fan intake area in the front grille. I don't see this mesh filter anywhere on the parts diagrams. Pic below (this is the drivers's side of the lower grille on a US spec 1987 car).

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The filter appears to be in decent shape (can still see light through it) but I would like to know more about it to determine the best way to clean it or replace it. Anybody know about this or have a part #? I half wonder if this was some sort of aftermarket mod since it's not on the Ferrari parts diagrams as far as I can tell.

Also, here's a pic of an old radar detector antenna I removed from the lower grille, it's been there from the time of the car's first owner in 1987. I also cleaned up a good 20' of cables and wires that were running between the front/rear radar antennas and the display unit in the car. They did quite a wiring job installing this radar detector system back then.

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