Yep. A blocked evap core can limit air flow. See pics below for descriptions
Pine needles in a 97. Not enough ro block air flow but this is how it starts.
Mold and crud in a 90. Alone, this will not limit air flow much but can produce a musty or fowl smell coming from the vents.
Rodent nest. This along with the crud can limit air flow.
You can vacuum out most of the lose debris by removing the Blower Control Module and using a vacuum with a long attachment with a small diameter. The mold and caked on crap can be removed with a foaming spray. I beleive there is more information in the Techinfo link at the top of the page