Hi - I have the EDX-2 working with an ICOM IC706. Works great.
Step 1 - you need to obtain a 4 pin Molex connector that is compatible with the IC-706 (which is 4 pins). The EDX-2 stock connector is 5 pins, as I recall.
Step 2 - Connect EDX-2 wires into the new 4 pin Molex connector as follows:
Pin 1 (the first pin adjacent to the pointed edge of the connector(<====)) : Green
Pin 2 : White
Pin 3: Red
Pin 4: Black
Step 3 - enjoy.
P.S. You should confirm that ATU connector outputs on different ICOM rigs are wired the same. I would guess so, but you may want to confirm this.
Feel free to e-mail me at email@example.com
if I can provide additional assitance. I don't look at EHAM forums all that often.