Ok, slight update on that, had another look and it all makes sense now.

The looms for a N/A EFI, OFAB and OFAC are all the same looms basically.

SO, the changes that should be made in your case from the standard EFI loom (assuming its a MK4 Escort EFI loom)

There is a Blue/Yellow wire running from Pin 28 of the EEC IV ECU, to Pin 2 of the E DIS 4 module, this should be cut, (check it has no continuity).

And there is a pin variation for the CO Pot (very co-incidental IMO seeing as you said your fault code reader keeps flagging the CO Pot). One of the Brown wires from the CO Pot (note there is 2 wires and one should be Negative/Earth) connects to either Pin 8, OR Pin 27 of the EEC IV ECU. The way i BELIEVE this should be (sorry the diagrams dont state which variations its for) is if your running OFAC or N/A XR3i it should be at Pin 8, and it running OFAB it should be at Pin 27.

IMO if i were you i would check that other wire is cut, and then try moving the CO Pot wire and testing with your fault reader again, certainly got nothing to lose by trying.

Oh and nearly forgot, a N/A loom doesnt have the connector for the AMAL valve on it, very easy to wire in, but not everyone runs one anyway.