There should be a slot on your carb slide that the Idle Screw fits into. Sounds like your carb slide is out of alignment with your idle screw. When you tighten the Idle screw, your carb slide should slide outward from the carb body opening the gap between the slide and the body and of course increasing your idle.
Try to find the slot on the slide that the idle screw is supposed to sit in and get the slide lined up and then tighten the idle screw a tad. When you get it right, the carb slide should NOT stick when the idle screw is tightened, and you should NOT be able to pull the carb slide out of the carb body completely.
If that helps? I had this on my first warhead as well...takes a little moving of the slide to get the screw back in alignment properly. Worst case, you can remove the carb slide, find the slot, and then re-install it lined up with the idle screw.