Idle mixture sounds too rich. Carefully, and in small increments until correct, adjust it leaner with the IDLE mixture adjuster. A slight readjustment of hi-speed mixture may be required when done. Once you get the idle mixture set, you should never have to fuss with it again. All future adjustments will be with the hi-speed mixture only. Be very careful of the prop if done while running. [:@]

See page 25 here for more guidance:
http://www.supertigre.com/manuals/sup-manual-v1_1.pdf

Pinch test mentioned works well on both needles.