Actually, Ohio, if you can get your hand up in there to pop the grilles out, it's a 20 minute job on the Boxster. They're made out of gutter mesh from Home Depot (high dollar Porsche upgrade). Cut them to shape and then install them by drilling small holes through the part of the grille that you can't see when it's installed (see pictures

) . Then screw the mesh to the grilles using small screws and those flat trim retainers (again, see pictures, and you'll recognize them). Pop the grilles back in and you're done. I did the intake vents also after desnorkling because of the possibility of sucking in birds and small children. If you want them in black, spray them black before you install them. Easy.
See where my leaves get stuck?