Wiper seals

Only way to get all the leaves, pine needles, and misc. debris out of the otherwise unaccessible cowl plenum is to remove the fresh air plenum boxes hanging down from the underside, then stick your arm(s) up through the now open holes with whatever tools you need (scrapers, sponges, scotchbright pads, garden hose, air gun, etc.), and manually clean them out. Being a contortionist with skinny arms, able to stand on your head and endure pain, would really help.

Mine were so bad it took me three sunny days to do. When I started the pine needles were so thick I couldn't even tell there was a lip around the openings to keep the water from flowing right down into the interior.

Don't forget to unplug the drains, as noted above.