get some fiberglass window screen cut it into 2 strips take off the grills over cowl, take off screws to fresh air ducts (but dont remove ducts), lay screen over ducts( put screws in thru screen, make sure screen covers the openings( trim to fit if neccisary), put the grills back on and voila you have a gaurd against debris. i put some washers on the screws to hold them in better but that is up to you. hope this helps someone...