We had this high-range dual Exhaust Gas Temperature (EGT) kit manufactured exclusively for us by noted aircraft gauge manufacturer Hewitt Industries. This gauge displays the EGT readings of both chambers simultaneously, so you can determine the balance of combustion. Oxygen sensor readings -- even those that are "wide band" -- only tell you if the AVERAGE mixture is okay; not what the leanest chamber is doing. This is why you always hear stories of people claiming their engines blew at a "safe" Air Fuel Ratio (AFR). If both chambers were perfectly trimmed it would probably have been safe, but that rarely happens. 3rd gen FD intake manifolds, in particular, are horribly misbalanced. The front rotor tends to go lean at low load/RPM and the rear chamber goes lean at high load/RPM. EGT can also give you feedback on ignition timing effects, which WBO2 cannot do.