The low speed screw is not really needle (which is tapered). It is either a plug which enters the spraybar at low throttle or a sleeve which slides over the spray bar; this type has a slot in the bottom of the bar as earlier stated. If either is too close to the spraybar at WOT it will affect the HS mixture by not allowing the HS needle to control the mixture, in other words it fixes the mixture usually at too lean a setting. Hope this helps to answer your question. In other words the LS setting CAN affect the HS setting; it also affects your throttle setting up to 3/4 or so throttle as it slides out of the spraybar.