As above, you don't needto change the loom, its a waste of time.
Unplug your two ecus behind the heaterbox andjust remove that wiring, if you cut all the tape off you'll see what to remove.
It'll be from the ecus to the fuse box, and then disconnect everything from the metering unit and do the same.You can remove this lot all round to the fuse box or for ease, just up to the passenger headlamp and leave the dead wires in, leaving the factory tape on there so looking neater.
Then use the fiesta engine loom, a live, earth and if you change your pink relay by the pedals to a normal relay, you can just wire pin 5 to ignition live also saving all the extra wiring ( if you don't mind the fuel pump running all the time the ignition is on that is )