It depends on what you are planning on running, a blow through is after the SC and a draw through is before the blower. If you are planning on just slapping on a S trim with no intercooler or anything you will want a draw through so it is mounted before the blower. If your thinking about running a procharger that is intercooled chances are you will want to run a blow through. You need to decide what you are going to go with for a supercharger kit before you buy things like a mass air. Oh and by the way, turbo.