The rolling road is a superb tool for diagnostics. We use a gas analyzer in the exhaust to monitor the fueling whilst the vehicle is running under load. We can run the car at any speed, any rpm and at any throttle position. We can determine if the engine is running rich or week under any conditions. The rolling road can also be used to monitor the ignition system. Here we assess the fueling of a Shelby Mustang GT500. This one was running a little weak but still making a lot of power.