Heat - A/C Blower

I replaced the blower motor in my 1989 Mazda B2200 a few months ago. It sounds like it is working perfectly, but the air barely blows through the vents on Heat and A/C.
I removed the blower yesterday but did not see any obstructions (or felt any).
Any ideas for my problem? Like I said, The blower is working fine and sounds like it is blowing a lot of air, but I'm only getting a little air flow through the vents...

Check those bands on either side of the evaporator case. They have foam on them that deteriorates to nothing. Once it's gone, they leak a lot of air.

Also, drop the lower portion of the evap case. Chances are your evaporator is clogged up with dust, carpet fibers, and often times mold. This will dramatically restrict the airflow through your system. You don't need to open the refrigerant system to do this so you won't need to evacuate and recharge the system. Just hold on to those clips as they will go flying. Also, put a trash bag or towel down in the passenger floorboard to deep all the crud that comes off your evaporator from getting into your carpet.

Yeah, check the evaporator for blockage, could even be crud from an evaporator leak, like refrigeration oil mixed with dust, that happened on mine a decade ago. I had essentially zero air volume coming out of the vents, even though the fan was spinning fine.

Also, check to make sure that the squirrel cage fan is securely attached by its set screw to the blower motor shaft.