Unequal Airflow From Upper Vents

[Sundown94]

Has anyone noticed the following, which I just discovered tonight after owning my H2 for over three years now. If I set the temperature on both sides of the climate control to be equal, then manually set the system so that the air only comes out of the upper vents, and manually turn up the fan to maximum speed, more air comes out of the passenger side vents than the driver's side. Even if I turn the knob and close the passenger side vent, more air does NOT come out of the driver's side. You may wonder why I was messing around with the controls and manually setting them in the first place, and the reason is because it was so damn cold out tonight that I wanted maximum hot air blowing on me (besides, nobody was in the passenger seat anyway). Any ideas as to why there is better airflow on the passenger side with all other things being equal? Thanks!!