There is an adjustment screw on your IAC, but it's not in plain view.
No, I don't mean the hex adjustment on your throttle plate.
On the top of your IAC, there is a hole that has a screw recessed into it.
Look down from directly above it (get your head in there) and you'll see it.
Put a flathead screwdriver in there and 1/2 turn counter-clockwise.
Let us know how it works.