I've done a homedepot grill cover. Cut out all the plastic inserts. Turned out to be very strong. Zip-tied the piss out of it. The only time i'd use the cover is in fowl weather. Learned to get the bumper cover on and off in like 2 min.

If i do a CAI, i'm cutting the plastic on the bottom of the car to get more direct air. To me the plus of a bigger filter and more direct air.