Pass side air leak under dash?
 

My little brother rode shotgun in my 96 up to Dad's for Christmas and he said he could feel a draft coming from under the dash on passenger side that was speed dependent. Not a bad draft but enough that his feet got cold even though i had heat on floor vents. I have not gotten around to corkscrewing my large hide up under there to see if there is an obvious reason so has anybody had a similar issue? I changed out the heater core maybe 10 years ago but haven't touched anything under there since so I a wondering what is up there that could be leaking air now. I am not getting any water inside that I am aware and after this past year of record rainfall I figured if there was a leak I would have had water issues in evidence.

Anybody have this issue and what fixed it?

There isnt anything to leak like that. The only opening is connected to the cowl which cant leak like that. What was possibly happening is the HVAC box has a door which remains shut during all the settings but the MAX AC setting. When you switch to the MAX AC setting that door opens and allows the fan to pull air from directly in the cab instead of using the outside air from the cowl. Maybe that door was open and allowing cool air to reach his feet since the door opening is right there at the passenger feet.