1984 cars have solid metal covers on each side, with a vent in the middle (which is made of magnesium) over the engine. I've been told that there is an upper and a lower vent, and that they are both removable.
From: Sketch
85-86 cars have a pretty heavy, cast metal louvre vent. In '87 they went to a stamped metal part on all models. GT fastbacks started using stamped metal louvres first in '86.
From: Derik Voigt
My engine covers always seem to collect leaves. It's really annoying trying to get all of them out with a screwdriver, so I tried popping all of the little clips on the back off instead, and removing the mesh screen underneath. Now, all of the leaves just fall right out. The only problem is, some of the clips tend to break occasionally, so I wouldn't do this too often.