Boost is a measurement of restriction. Like grey said a smaller s/c pulley will make it spin faster shoving more air into the engine creating more restriction. It has nothing to do with the fuel injection. Now, if you change your intake to a better one, you might in turn reduce the amount of boost because you are reducing the restriction while still making more horsepower because you are putting more air into the motor. You should just read up on the subject, you should be able to find numerous articles using the search feature.