AEM 30-4100 UEGO Controller Gauge Ideal AFR monitoring tool for EFI and carbureted applications, and engine dynamometers Does not oscillate AFR reading like narrow band sensors Reads in AFR or Lambda via a switch in back of gauge housing 24 Color-coded LED display lights provide immediate reference to engines air/fuel ratio (AFR) or Lambda ratio Included bezels and face plates allow you to personalize the look of your gauge