I would suspect one of two things: Either you were given the wrong IAC, or the internal spool valve was jammed out of place when it was installed or you have an air leak.
I would remove the IAC and look inside. There is a shaft that moves back and forth to vary the amount of air allowed to flow. The shaft has a disk on it that blocks or opens by moving within the IAC. If it were to be stuck, it could not close and you would have the high idle you reported. Try checking to see that the valve gizzards can move.
tom