Hot intake air, when idling (for a trafficlight) is bad too, because when the light turns green you want to have 'performance' again. It doesn't help if your engine then "pings its brains out" because everything is hot and heatsoaked again...

I've been thinking about insulating the cold air ducting to the engine, as enginebay heat also warms up the tubing.
A double wall tubing should help in keeping the incoming air cooler longer I would think. Also applying a heatreflecting layer on the tubing should be helpful I guess.