As usual, the Mini Cooper S with the Eaton M45 supercharger also has a bypass valve, which helps with fuel economy and lighten the load on the supercharger during idling (for instance). On NAM (North American Motoring forum) I noticed a popular mod, which is also known as the VGS or Vacuum Gain System modification.
Basically, the VGS mod changes the way the Bypass valve is operated. From indirect vacuum to direct vacuum, allowing faster response of the butterfly valve, but also keeping it shut better so no boost is lost.
I liked it in the beginning, but it makes for a rough driving experience. So in the end I reverted and never went back. Thats why we experiment 🙂
Changing the vacuum line routing.
Brand new Bapmic Compressor Bypass Valve (CBV).
Modifying the bypass valve.