By default, the core MIDI interface is running at the standard MIDI baudrate (31250), for the to-COM option you need another baudrate (38200) which has to be selected in the ID header of the PIC during programming the bootloader. Mike used the standard ID (000000000000), so MIDI baudrate is selected
Without a PIC programmer the only solution to change the baudrate is the use of a standard MIDI interface (if you don’t have one, you could maybe use the gameport, see MIDI trouble shooting guide for schematic).
Then upload MIOS, and use the change_id application in order to enable the COM flag