Carrier 9200 placed in crawl space (aprox 3.5' height) 5 years old, blows good, low amount of heat being generated. Same unit for main level, no problem. Filters good,

What can effect the heat output?

Low heat can indicate many different problems

Low gas pressure at the unit

Defective gas pressure regulator in the gas valve itself not allowing proper flame volume.

Weak limit control allowing the furnace to shut down before the proper temperature is reached.

Most if not all of these items are not user friendly to diagnose or repair.