COR or circuit opening relay, opens the fuel pump (+ve) feed once the ecu detects a constant rpm. (I believe) either way, the ecu knows the engine is running.
Circuit opening relay is a 5 wire relay. One out to the fuel pump, blue with black trace, a green with red trace wire from the ecu (open signal) a white with black ground wire, a black with red switched power feed from efi main relay and a black with white from the starter motor switch.
Circuit opening relay is highly recommended, as it prevents the fuel pump from running, if the engine is shut off in the event of an accident etc.
On my small port loom, the COR was mounted to the top of the unit, also in a bigport AE82, its in the same location, however I think it is mounted somewhere not on the case but in the near vacinity.
I can send you a photo of a COR and the little plug which plugs into it, but apparantly people in SA are jerks...