yes, cold air improves engine performance sa car, as hot air is builed up inside the engine while the car is running, so in theory, the colder the air that is being taken in by the engine, the better! Dili lang ko sigurado kong better ba na sa fuel economy, kay in my own opinion, the better the performance, the more gas the car consumes? ambot.
ako, akong awto kay Nissan Skyline, I have placed a cold air intake dapit sa bonnet, arun maka sulod ang cold air while mag dagan akong awto, it helps performance but hardly noticeable, samot pud kong turbo inyong awto, parehas sa ako *suyop ang gasolina*

..
im not sure if it shows u guys o the pics, pero mao na akong cold air intake gi istall:
