Sounds like everything got some paint or overspray during a repaint of the car. They likely shot all the panels in place and the paint passed through all the vent slits in the coil cover. Basically all these parts were finished as you might have found them, just look at the bottom side of the shield, bracket, arms ....
This sort of thing is real common on these cars after all these years
Note to others viewing this thread - other models (non-Shelby's) can be finished in this area will appear different.
As yours possibly looks at the moment - Not original
Original without the repaint overspray