Koso X-2 Multi-Function Boost Gauge With Air / Fuel Ratio Maintain optimal performance and safeguard your engine with the Koso X-2 Multi-Function Boost Gauge. This essential tool monitors boost, air/fuel ratio, and temperature, all in one compact unit. It's designed for machines equipped with forced induction, ensuring the air/fuel ratio stays within safe limits to exploit your engine's full potential without risking damage. Ideal for those seeking peak performance, the Koso X-2 allows for real-time monitoring, critical for maintaining engine health and efficiency. Features: Digital boost readout Air / fuel ratio display with wideband O2 sensor Compatible with 2 and 4 stroke engines Indicator lights for rich / lean conditions Requires a 12v DC power source