Think I figured it. There was a very small machine screw (from where or what I do not know) that somehow ended up sitting on the cowl and miraculously wedged itself perfectly to fill the drain hole in the passenger side cowl drain hole. So perfectly, that it looked like it was supposed to be screwed in there. Debris had built up around it creating a perfect seal. When it rained, it rained buckets, and probably backed up and overflowed out of the depression there and straight down into the passenger fresh air intake.
Of course, I had already started to remove my plastic cowl parts by this time to make sure it wasn't an internal problem and, since the numb nuts who installed my replacement windshield managed to get it glued in a few spots with windshield adhesive, a couple of the molded on clips broke off...... So now I'm patiently (ha) waiting for new cowl parts to arrive in the mail. On the bright side, at least the inside of the cowl area is now very clean.
**ScoobieDubie, just about every car uses a similar two-part cowl setup. So I wouldn't blame Japanese engineering. I actually have heard more complaints about GM vehicles of the last 15 years or so having issues with leaking into the passenger compartment.
Edited by SmashedGlass, 19 March 2014 - 08:39 AM.