I don't mean to sound confrontational, but why do you think that the number of turns of the mixture screw is critical? Based on the diagram and description in the Model B service manual, it appears as though the mixture screw controls the amount of fuel available to the engine when the throttle plate is nearly closed, at minimum idle speed. As the throttles is opened, 3 more ports are uncovered to add fuel for the transition to part throttle operation. I'm willing to believe that the additional air coming through my PCV system is affecting the operation of these 3 ports by causing the throttle plate to be too far closed for 600RPM idle, and thus is partly repsonsible for my slight hesitation coming off idle. but I just don't see how the mixture screw plays into this. It seems like anywhere in the adjustment range should be fine, as long as you can get the right mixture for the minimum idle position of the throttle plate.
regards,
Leon
