[ischmitz]

One possibility is that the input for the CHT sensor is damaged so your ECU "thinks" it is dealing with a stone-cold engine while the engine is at operating temperature.

Also, expanding on what Ab54666 mentioned. The fuel quality switch is nothing but another input into the ECU. So even if it is all the way counterclockwise in position 1 it still could be misinterpreted by the ECU if the corresponding input is damaged.

A real test would be to compare your ECU to a reference ECU by measuring the fuel pulse length (mixture strength) for a given set of sensor values. This can be done with about +- 2% accuracy.

Ingo