Help- I have a RT Carb High Performance 15 mm, purchased from thatsdax.com, that with the idle screw completely turned out, and the slide totally closed, continues to idle at approx 1500 to 2000 rpm. This carb maybe has 75 to 100 miles on it. I cannot find any way air/fuel is getting past he slide. Help please, I need to slow this down. Thanks for any suggestions.