The trick is to cool the air while not disturbing the intake velocity. This is kind of tricky with a NA car because the flow loss/disturbance will cancel out HP gains from the cooler intake air probably. There are a lot of people who do this with air to water intercoolers, and make an ice box around the intercooler core. Basically the water reservoir is around the main core instead of being an auxillary tank somewhere else, etc. Bypassing the water to air heat exchanger in the front wouldn't hurt either while you use ice in the box..