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.