Forge Motorsport BOV / Diverter Valve Spring Tuning Kit - FMDVTUN Now you can fine tune your Blow Off/Diverter Valve to the exact needs of your engine with this complete tuning kit. The valve tuning kit includes four color coded springs. If you are finding that the valve is dumping more than required or you are loosing boost pressure it is normally an indication that a stronger spring is required.