Required when installing L&M NSR cams. Specially modified BPV opens at very low vacuum levels. Required for proper idle quality and tuning with L&M cams. 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.