This probably accounts for the sharp drop in temperature when you're revving due to the stark contrast between the cold winter air and the accumulated hot engine bay air.
Agreed. I didn't look at your graph initially as I thought you were asking about normal running temperatures during steady cruise. Obviously, if you increase engine and/or vehicle speed sharply, this will draw a slug of ambient air into the intake tract and IAT will drop noticeably until it equilibrates again with the warmer air in the engine bay. I don't know what the response time of the IAT sensor is, but in the millisecond range I should imagine.
TTQS
