Dan:
I've read the suggested thread but I saw no mention of the vent. Where is this vent located?

Dan:
Where is the vent you mentioned located?

As suggested, I cleaned the evaporator and ensured that the evaporator case drain was open. I also caulked around the air intake duct under the cowl cover. But I'm still getting water leaking into the passenger footwell at the location marked by the red arrow in the photo. The water is leaking from behind the foam insulation pad, against the firewall. Any other suggestions as to the source of the leak? Would it be worthwhile to remove the dashboard?