Let's try Device 20, which is used by the Tuner in the Complete series.
Assign Setup Code 21781 to the AUX button. To test any of these EFCs, tap Setup (don't hold it) and enter the 5 digit EFC. When you enter the 5th digit, the IR signal will be sent to the amplifier.
vol up 37497
vol down 37501
mute 37389
Power 37385
If these work, assign them semi-permanently by
using the 994 Command.