Lastest from a reliable dyno source is about 80 horsepower per psi of boost added from ram air. About 2 psi of added psi over 200 MPH in a forward facing injector hat. For a normally aspirated engine that is about 160 HP more from speed over 200 MPH. For a supercharged engine with a 2 / 1 blower boost ratio, that is about 320 HP from ram air. More info about HP & boost in FIRS & 5HPM.