One other comment for the original poster:
While YF's can be used successfully in a multiple carb environment, other carbs can be more easily adapted; as the YF has a vacuum power system.
Thus when introducing YF's into a multiple carb environment, adjustment is much easier if the various springs (which fatigue) in the vacuum power system are replaced with new. Generally, these springs are mail order only.
We suggest that carbs with a mechanical power system (such as the Carter W-1) be used in a multiple carb setup; or change all of the spring.
Jon.
