What was it I heard? 2 HP per 10 deg F reduction in IAT's?

Something like that...

And as I recall, I measured temps of 145-165 underhood (engine bay) @ 75 MPH on a 90 deg day. 125 degree IAT with the stock airbox. So, if you can get pure 90 deg air to the intake manifold, that would be a reduction of 35 degrees. 3.5 X 2=7 HP gain.

155 degree (65 RISE) air WILL LOSE YOU 13 HP. 6.5X2=13

As I recall, but I'm getting old!