The Mach 2 is configured as a 100% recirculating valve (i.e. bypass, plumb back) and add on kits are also available to convert to 100% atmosphere venting. Use the recirc model for direct factory replacement when you want the performance WITHOUT the noise! Add the conversion kit when you want some noise with your performance!
Factory bypass valves have two main shortcomings – one is that they are typically designed to start opening above a certain pressure to protect the engine, an. . . Show More >