Whats wrong with turbulent air?
You actually want some turbulence in your intake air.
As for the intake itself..how do you figure that metal disapates the heat better then the plastic? The metal intakes take heat from the engine compartment itself and heat the tube..your not going to heat the tube from the inside just by moving air, if it does, its very very minimal. Dont forget, where talking about air thats at atmospheric pressure, not compressed air.