Required when installing aftermarket camshafts. The top port must be referenced to vacuum and boost as the boost source will close the BPV since it no longer has a return spring. The bottom port is no longer used. Specially modified BPV opens at very low vacuum levels. Required for proper idle quality and tuning with L&M cams. Necessary upgrade when using most aftermarket camshafts. Direct replacement Bypass valve for Eaton superchargers such as the VMP 2.3L TVS for Cobra, GT500, and 5.0L. Fits Roush superchargers. Also fits stock M122 and M112 superchargers found on GT500 and Cobra. Fits Gen3 and Gen3R. Fits Odin.