So, update, I'm considering bailing on these. I didn't notice this earlier but now that it's been raining and I've had windows up more and defrost on more, I've noticed the fan now makes a whistling sound at higher fan settings when not on recirc. Not willing to deal with that to save a couple pounds. Working theory is there's so much less resistance to flow that it's pulling air quickly enough to cause the whistle. Trying some things with tape to see if reducing flow through the filters might make the whistle go away. It was whistling above setting number 2 with no tape, now it doesn't whistle until 4 with them about half-blocked. Whistle filter deletes go woo woo
