I love asking the homeowner ( when did you change your filter last ) and they say uugghh what filter, usually after living in the house for years never thinking about it or knowing it needed it
I remember the high efficiency filters I sold after another one of these invariably inacessible without removal to clean chemically jobs, the 99 cent jobby see through filter seemed a joke and easy sell, later i find with a Honeywell E nalysis setup that the pleated 3m or equivalent high efficiency filters reduced air about 4-500 cfm!, I say use them in winter, but in summer if it seems to be choking, open it up with a cheepie, or god help us , nothing to pull down the room quickest, maybe K&N flters should make cold air intakes for our houses too, lol.!
I had a customer tell me I was full of it that there was no filter for the a/c. She took me out side and asked were is the filter. I told her is uses the same filter that the furnace did. She didnt belive me untill i proved it.