A quick scan of the electrical diagrams for the ECM shows no difference between 2WD and 4WD. However, there IS a difference if you have an automatic transmission. The TCM (Transmission Control Unit) has an additional input for 4WD. This additional input comes from a switch on the transfer case. This signal tells the TCM when the transfer case is put in 4L to change the shift points in the tranny. But since this an input to the TCM and not the ECM it should not cause a problem.

But what year is your Sportage? If it isn't a 1997 the ECM that was installed will not match and you will have "ghost" DTC's. 1997 was a unique year as far as certain components are concerned. It is vastly different from 1996 and 1998 - 2002 had other changes.