The thottle valve switch has two circuits - WOT and idle with a common ground. I don't recall which circuit is which, but with the valve closed one should be open and the other closed and the opposite at WOT.

If the idle signal circuit misbehaves, the car will not idle properly because the idle system never knows the engine is idling. It will usually idle high. When it misbehaved a couple of years ago on my car a thorough cleaning of the switch and connector restored it to proper operation even though neither appeared at all dirty.

The throttle valve switch has no effect on the EHA duty cycle as long as the switch sends the proper idle signal. The screw and locknut throttle valve stop can be adjusted if the idle control valve duty cycle is not in the correct range.

Duke