Uneven air pressure from windshield defroster vents

[E.D.75GMC]

So I have a 1996 K1500 with A/C, and it's been raining a lot here lately so I've been needing to use the defrost at night when the temp drops. Anyway, I've owned the truck for a year now and it's always been like this, but there's almost no air flow through the drivers side vent at the base of the windshield. The passenger side vent has very good air flow but you hardly get anything through the drivers side which doesn't help much when your windshield is all fogged up. Has anyone else had this issue? I know the blend door and whatnot is functioning properly so I'm leaning towards a piece of the duct work has come out of place.

[sntrym95]

The vent piece behind the dash is one piece, so unless it's cracked, it's likely something fell in there. Dash removal is pretty easy, you just need to lean it forward to look down in there.