I would think the IAC motor would keep the idle up to 750 rpm under all conditions "IF" its functioning correctly.
In that I mean, not worn out or excessively dirty and "Add" on top of this, about "not" having vacuum leaks from other sources.

What needs to be done is to reset the the throttle body system to the basic idle setting.
This means a clean throttle bore, properly set position switch and the throttle stop screw not holding the throttle plate open to far. In most cases I have found that about one-third turn of it after it has "contact control of the plate" is enough.

In most cases you should be able to make the engine almost stall by using the blue/ pink wire connector to ground. This makes the IAC inoperable. Check it out in the manuals and make sure to use only one of the wires out of the connector, connected to ground. I forget if its the pink one or the blue one you DO NOT want to use!

You want the throttle position switch to click properly with the plate closed as much as possible with that tiny stop screw under the opposite side.

In most cases, if you have that large black knob on the throttle body, it will be almost completely closed or open just enough to get it not to stall.
For the most part on the LH system it is useless and can only be thought of as a fine adjustment, of the final closed position, of the plate.

Upon releasing the grounding of the IAC connector, the engine should jump up "very slightly" in RPM's and hold that 750 rpm upon loading of a transmission or A/C.
Actually the computer may kick the idle up even a bit more with the A/C on "if" its in the program of certain cars. I have never seen anything over a thousand RPM's being used or there was something else out of kilter!

That's almost like, out of whack! Might be almost like not having that V8 juice on T.V. Commercial!
Or having a V8 dropped into a Volvo for another type of kick! (o:)!? (:-)
ANYWAY....
This puts the throttle plate at the lower range of the opening and closing of the IAC. By having it reset, there should be enough range left to raise up the engine speed, under a load, to keep it at 750 rpm.

In both cases mentioned on these posts one is to high and the other is to low of the range of the IAC motor. The throttle position switch, is "telling" the computer, I want the engine to idle NOW, with no stalling or pulling me down the road!

Oh! by the way, the throttle switch does not have lips but it's got your toes! (:-)
Just my thoughts, hope it helps.
Phil