I can not emphasize enough the role of the transition slot, and the positioning of the throttle blades along that slot, in getting your engine to run right. You have a big FE, a healthy cam that lowers your vacuum, along with hot under hood temps. If you have your throttle blade up deep in to the transition slot, then you're negating the effect of the idle mixture screw and actually defeating the whole purpose of the transition slot to begin with. The transition slot is really a beautiful little engineering design. When your throttle blade is down at or below the bottom of the slot then the slot is actually feeding fresh air in to the emulsified fuel. But as you open the throttle, and the blade moves up the slot, the portion of the slot that is below the blade grows larger and brings in more pure emulsified fuel instead of air -- it "transitions." It's a beautiful, simple design.
