1990 Other Volkswagen Models engine idling high

Well I dont believe there is an idle screw, but I could be wrong, what I think is happening though, is you have a vacuum leak, check all hoses for disconnection, and cracks, if you cant seem to find it, then get a can of carb clean and gently mist it around the vacuum hoses and the intake manifold, if the idle surges then that is the approximaty of the leak and look in that area, holes and cracks can be very deceiving, so look good, and that whistle thats probably where your leak is, it will make a whistle sound when you have a leak too