Idle Air Control step motor; screws into the right side of the throttle body. Big fat thing, takes an 1" wrench to loosen if I remembr right.
A 'bog' or hesitation is caused by the mixture being way too lean.
The IAC's function is to set the mixture when the engine is cold and before it goes into closed loop. However, if this thing is 'mechanically' stuck in the open position, it would act must like a vacuum leak in closed loop.
Not saying this is your issue, just trying to help you eleminate another possibility. Does the engine idle too fast? Higher than about 600 rpm ?