I don't know about that Holley, but some carbs have a choke pull-off piston there, operated by vacuum. When the car starts the vacuum tilts open the choke a small amount.
Thanks, KitCarlson. I needed to know the name of it: "choke pull-off piston". Holley failed to include the part in the instructions or exploded view. I theorize that it's only one the 870 Street Avengers.
