errrI take it youve put the whole XR loom in then?
the fault unit is for the lights out thingy on the XR dash and the other i've no idea but the only leccy thing they have is an igniton amplifier for the leccy ignition the injection is all manualy done.
have you tried on interford? there are quite a few xr4i owners over there
http://www.interford.co.uk/forums/