A fuel control system for a gas turbine engine that includes a primary fuel circuit, a fuel tuning circuit, a plurality of combustors connected to the fuel tuning circuit, oxygen and carbon dioxide sensors in the exhaust stream and a feedback control loop operatively connected to the fuel tuning circuit and to the oxygen and carbon monoxide sensors which serve to control the precise amount of fuel and air being fed to each one of the plurality of combustors in the engine. A parallel array of control valves in a tuning fuel circuit connect to corresponding ones of the plurality of combustors in the gas turbine engine. The fuel control system thereby “fine tunes” the amount of fuel and air being fed to each combustor using data regarding the detected oxygen and carbon monoxide concentrations in the exhaust gas as provided through a feedback control loop.