2005 Ford F-150 ProCharger Kit - Picking Up the Pace
The bybass valve is used to bleed off boost during part-throttle situations. It mounts downstream from the MAF sensor so it's not necessary to reroute back into the inlet system as the expelled air from the bypass valve is "non-metered." If it had already passed through the MAF sensor, then the air would need to be recirculated. View Related Article