Throttle body.
 

When you replace a mechanical throttle body how do you set the stop screw and IAC on a 94 f15.0 ?

There is nothing to set really, the stop screw should already be set to just stop the throttle blades from binding in tbe bores, and with the engine running and IAC disconnected the motor should be right at the point of stalling. When the IAC is connected the motor should settle into a 650-700rpm warm idle.