AEM Wideband Digital Air/Fuel UEGO Gauge (30-4110NS)An AEM Wideband UEGO Gauge is a wideband sensor controller that monitors air to fuel ratios (AFR) as you tune up your car. The goal of using the device is to prevent a lean fuel mixture that may damage the vehicles engine and prevent a rich fuel mixture that decreases performance. To improve AFR accuracy and control, AEM combines its single channel wideband UEGO controller and gauge display into a single unit that features a user friendly interface.