I want to improve the efficiency of my A/C. A significant problem in the
summer is the amount of air leaking into the cabin through the vents intended for
heater output. The worst are the vents near the floor on both the driver and
passenger sides.

Has anyone found a solution to this problem or even attempted to address it?
Before I dive into this, I want to know if it's a big project or a relatively
minor fix.

Thanks in advance to anyone who can offer any help.
Dan R.