I have modified my air filter box to be a "non-constant" temperature device.

The thermostat that operates the lever stopped working on mine many years ago.
I've gone a few winters without it altogether. Actually took the entire front piece off the air cleaner box.

But last year I rigged it up so I could at least grab some warm air. I lifted the flap about 3/4 the way and drove a screw through the side of the housing to hold it in that position. Springtime comes and I remove the screw to get all cool air. Not quite automatic like the thermostat would be, but it works.

I find that it does run a little better with warm air when the temps are below 20 degrees (F) or so. I also am using HIFs.