ok, i changed over my ECM on my 84 to an 87. thought maybe my maf was bad, since i was gonna buy a new one figured i'd change over to 87 ecm. got ecm out of salvage yard along with mat sensor. new maf sensor. when i first got it going everything looked fine maf reading was 5 @ idle. then all of a sudden car started running rough putting out black smoke, want idle no lower than 1025 idle screw all the way out. think maybe i got a vacuum leak? or could the IAC valve cause this? thanks for the replys,