While peeking around at the various DX7 firmware versions I was able to identify the code that is responsible for the DX7 transmitting $FE (MIDI Active Sensing) constantly. I did not have the time to look at adding a menu item for it, so I just disabled it. If anyone is disgruntled by the DX7 sending MIDI $FE (Active Sensing) then this will alleviate your pain.
This link points to the updated v1.8 firmware that I renamed v1.8a:
This link points to the updated Special Edition ROM firmware, SER7, that I renamed SER7a:
One other issue that kind of irked me about the DX7 is the burst of MIDI Note-Off events and controller settings that occur at power on. I haven’t had time to sort that out yet.