like he said, the fins would heat up to the underhood temps.

a sprayer might not be the best idea for the intake manifold because spraying cold air on hot things makes them tend to crack...you wouldn't want to be spraying cold liquids around in your engine bay.

The one nifty idea I picked up on at a porsche club race day was fitting a type of "ice box" into the intake track that you actually fill up with something cold, like ice or co2.