Okay, so I replaced my cowling with a new one (with all tabs and molding strips intact), and added some sealant where it meets the windshield molding strip for good measure. Cleaned and inspected everywhere I could see and reach up in the cowl and along the firewall before installing that, to include the drain holes at the corner pockets of the cowl shelf. All that seems good, no longer have water leaking down through the fresh air intake.
There is a trickle of water running down inside the cabin (again!) where the firewall meets the passenger side sheet metal, up and behind the heater blower housing!!!!
I'm at a loss as to how next to proceed. Pull the pass. fender off and check to see if there is a plugged drain in there (lower than the cowl drain, and inside the body)? Rip the dash out? Or can I get the heater blower housing out without pulling the whole dash?