ECU Wideband not matching Dyno o2

Hi, i'm tunning a gemini with a Emtron Kv8 pump 98 fuel using a bosch wideband 4.9 sensor wired directly in to ECU, using same wideband with dyno, ECU Lambda is not matching the dyno lambda Emtron is reading .600 lambda on one run the dyno is reading .800 lambda you would expect the plugs to be black if it was at .600 lambda plugs look fine, i've changed widebands looked over the setting in the emtron all looks good dyno o2 has been checked with other cars.

Any help would be much appreciated.

What happens if you switch sensors between the dyno and the ECU? Does the dyno show richer? If so, I would replace that sensor.