Yes, that cowl vent is one of the veeery few design flaws in the pre-86 200 series. Water from that vent flows in a box section channel down the lower part of the A pillars, into the rocker panels, and out through the four vents along the bottom of the rockers.

So also does flow leaves, pine needles, bits of airborne flotsam and jetsam, all to go into the channel, get stuck, get wet, rot, rust, and generally make a mess.

When I changed out my wiper motor I got into that box channel. Bought from ACE hardware the longest angle-tip tweezers available, and went to work with a crevice tool on the vacuum cleaner. Pulled out what seemed to be a bale of stuff.

Another way: Pull front and rear sills. Peel back carpets. Open the access hole covers. Go into the rocker panels with a vacuum using a small diameter hose.

An idea I am toying with: Go into the rocker panel with the output end of the vacuum. Heated dry air. It may not blow everything out, but it should loosen the stuff up and facilitate it's flowing on out.

Another idea: Use a big shop vac on the cowl grill. Cover the entire grill with a reall thick piece of something flexible, like a big cut from an old innertube, or heavy cinyl. See if anything gets sucked out.

Another idea: Identify a chemical which will not harm paint but will dissolve or eat away and leaves, pine needles, etc. Carefully flow some in. Remember that the channel also flows air into the heater plenum. That's why there's leaves around the back of the heater box and slid down under the carpets.

ONCE the channel is pretty clean, install a leaf shield, sold by IPD. It was about $47 for me, looks OK, and ends that worry.

Good Luck,

Bob

:>)