Okay, now it's time for a dumb question: why do we need input signals from
the power steering pump and air conditioner?

We already have input from the Hall sensor telling us what the engine speed
is, and if it's too low we increase the idle air flow & if it's too high we
decrease the idle air flow...who really cares whether the change in idle
speed is from AC, or PS, or from a belt driven coffee grinder accessory
that someone has installed.  If the throttle valve is closed, then adjust
the idle air flow to keep the rpms within a narrow range.  When there is
partial throttle, keep the idle air flow at a moderate level to avoid
shutting down the engine if the throttle is released suddenly.  What's
wrong with my thinking?

Brett