-The air valve shape. On the prod carb, the top 1/2" of the AV is bent over slightly. On the CS, it is straight, no bend. Have wondered whether straightening the bend in the prod carb would increase airflow slightly &/or affect A/F distribution.
From what I understand the divots are there to maintain the pressure on the air valve as the air valve approaches the vertical position the force is diminished so a flat air valve may cycle between seeing force and no force causing variations in airflow and AFR.