This is just wild theorizing...That sucking noise you hear near the intake may be a vacuum leak in the flame trap area. (Oil trap, PCV system, whatever you want to call it.) Check closely for any loose hoses. A significant vacuum leak may be causing the idle control motor to "hunt" giving you an unstable idle speed.

With the miles you have on that car, it would probably be a good idea to clean the flame trap, throttle body, and idle control motor. Also see what is causing the sucking sound. It could be a leaking hose or gasket at the throttle body or intake manifold.

Do the free or cheap stuff first.