It makes sense to me that the acc pump shot will need to be quite different between the 40% and 60% progressive linkage settings. The amount of additional airflow when the secondaries first open will be different on a percentage basis between these two cases. With the 60% linkage it appears that the initial crack of the secondaries did not cause a significant lean hole before the secondaries mains starting flowing since the additional CFM was a small percentage of the total CFM. With the 40% linkage, this transition happens at lower total airflow thru the carb and therefore the impact of the secondaries opening is bigger.
