N2O aka nitrous is used to and oxygen to the fuel mixture. The more oxygen the better the fuel mixture burns= more power. In a turbo/ super charged setup, lower amounts of N2O is used to and oxygen but, the main advantage is to aid in cooling the Intake
charge making the turbo/super charger more efficient. Just spraying N2O on the intercooler will have a very minimal effect and be a waste. Spraying cold water on the intercooler; as the new Lancer EVO does; would be beneficial.