Please try the following EFCs with the unit turned on to see if they will toggle power, or turn it off:
Test in Audio mode, with 1254 as the setup code. Tap Setup (don't hold it) and then enter the 5 digit EFC. When the 5th digit is pressed, the remote will send the IR signal. Holding the 5th digit will cause the signal to repeat. To verify that the procedure is correct, first try it with 51988. That should turn the volume down.
If one of these functions as Power toggle, you can assign it to a button (unfortunately not the Power button-- use Live instead) using the 994 command