I've got a 91 EF sedan, I have a Single Cam ZC and it wired to an OBD0 PR4. I had let a friend use it while I was gone and when I got it back there was a shit ton of problems with it. Needless to say $1100 later I have ironed everything out (i think). I had to put a new single cam ZC and trans in because he had blown the other motor, and then he had some air-headed mechanic replace the head-gasket and re-wire a few things. Well in the process he unwired one of the injector wires...anyways, without droning on, I haven't been able to come across a wire diagram that shows which wires you need to switch between the daul cam ECU and the single cam engine. I remember when I orignally re-wired it to MPFI and used the PR4 I had to swap some wire for the single cam motor (so it wouldn't use it as it would a daul cam). Hope I am making enough sense for some help. Thanks.