honestly ive no idea, i think they are pressured. i know they arnt electronicly controlled. however ive had to give up on the project as it will give me too much hassle becuase i will have to re-port the manifold to get it to fit. nevermind eh. Im still planning to run it on bike carbs at some point but for now ive used the rubber plenum off the injection system to house a pipercross cold air induction filter that i got off ebay so ive got a few more horses. i also got a chance to clean my inlet manifold freeing some horses up.