cold air requires less octane , cooling the air whether by a larger i/c or alky still has gains , then theres the pressure drop that witha good FMIC cmpared to a stock ic might be as much as 4psi , meaning you dont have to heat the air as much to get the same boost , colder air makes more HP and will require less octane so you can usually turn the boost up , not uncommon to see some pump gas cars with good FMIC able to run near 20psi