YOu can try this little trick, take the air bleed completly out of the intermediate and high speed circuits. This should effectivly dissable them or at least desensitise them for idle tunning. If for some reason the throttle blades are open to far, it can be taking fuel from the intermediate circuit. If removing the air bleeds from those circuits makes it better, you may need to go up on the intermediate air bleeds.
Allan G