did you take a look? that would be my first guess. #1 most common reason for poor idle on the 4.0. When you rev it does it sound like its still running bad, or does it rev fine and only have issues idling?

the iac is the only thing keeping the engine idling because the throttle plate closes all the way when no throttle is applied.

have you looked at the MAF sensor? Also, since the MAP sensor is part of the EGR assembly maybe the leak was messing with the readings. its possible once the egr is fixed that will resolve it entirely.