I think you’re mis-understanding me. MTH told me the WiFi unit (powered by a wall wart) is powering the TIU board thru the USB. The Z4000 I have is plugged into the TIU fixed IN and OUT jacks I use for my track power. I have been running It that way for about a year now. The AIU is the new addition.
I’m 99% sure the cord was only plugged into the TIU IN port and not the AIU OUT.