Air Fuel Ratio Gauge Install         I've completely forgotten who made this gauge, but it shows injector duty cycle V. S. Air/Fuel ratio. I only have the Air Fuel ratio portion hooked up, but I'm skeptical about the #s on the device as narrow band sensors can only measure in a narrow range around stoichiometric (14.7:1) This switch mounted close to the driver's fuse box feeds the left, right, or both sensors into the gauge.