Since this box is not a dual zone box this is a puzzler. How is the heat at the vent on her far side? As jeepco said, it could be due to the outer tube being off acounting for the reduce air flow. But not those flex hoses. I believe that they are just for the demisters and only flow air in defrost mode. If you look at Brents picture you can see that they hook on at the defrost plenum, not the main box. There are hard plastice channels that are hooked to the back side of the dash to go out there. (IIRC?)The air goes in the box, throught the evap coil then through the heater core. The blend door positions itself to control whether no air, all the air or just some goes through the heater core to be heated. Hence the term "blend air system". The blend door is vertical in the box, and the door for the dash vents is horizontal. I cannot recall if there are baffles in between the two like a dual zone system has. If there is you could have something in the box restricting hot air just affecting the one passage.