O2 sensor, vacuum gauge, tachometer, and an accurate record of fuel consumption on at least a 10 mile closed loop test course, and adjust the raw data from several test runs for temperature, atmospheric pressure, and humidity. Some of my really impressive dyno runs turned out to be a fluke of weather, not some magic we conjured up with fuel mixture and ignition timing. One of the best indicators of what's happening in the combustion chamber is an accurate record of exhaust port temperature. On the dyno, we had sets of exhaust manifolds and headers with thermal monitors for each exhaust port.
Jerry
