The cowling is the body panel that sites between the back edge of the hood and the bottom edge of the windshield. It is the section with holes for the wiper arms and motor and has vents in the middle for air intake to the heater blower.

The grate in the vent has a tendency to fall down and in, allowing larger detritus to get into the space beneath it and work into the rockers. It never worked all that well to begin with (littler stuff still falls in), but without it anything gets in there.

There is also a plastic cover over the blower intake that can fall down and let water in. Said water can fall into tehblower, freeze in the winter, and cause your blower to burn out or short if you turn it on. If you pull the cowling make sure to check that that black, plastic cover is firmly in place (you may want to epoxy it).

BTW, the cowling is removed from the engine compartment. There are four large screws that lock it into the firewall. if you remove those screws you can lever it out (pull it back towards front of car laterally, then lever it up and off). You'll need to remove the wiper arms and the associated rubber booties before doing this.

good luck,
rt