The stock K04 turbocharger comes from the factory with a rubber diaphragm and spring type design valve which can crack or become brittle from overuse and age, by installed our piston style valve you not only increase the durability but it also has an enlarged recirculation area to accommodate the increase boost/air flow from a tuned engine to minimize boost spike. The CBV is fitted with a "Stock" spring (green), capable for up to 14.5 psi boost. A "Tuned" spring (yellow) is also included for up to 23 psi of boost and is recommended for cars running an ECU upgrade.
