How to adjust the power level on Vaillant Ecotec

Older ecotecs with 4 circular buttons and 2 temperature dials

Press ‘i’ and ‘+’ button
Press ‘i’ key when D0 is shown ( if not shown scroll to D0 using ”+’ and ‘-‘ )
Using ‘+’ and ‘-‘ adjust the power level
Press and hold the ‘i’ approx 5 seconds until display no longer flashes (this saves to memory)
Press ‘i’ and ‘+’ button to exit diagnostic mode, alternatively do not press any key for approx 4 minutes