I saw that too, but Olei said he saw the choke open further upon firing.
Might be internal - as shown in Fig 15. http://documents.holley.com/199r8378rev.pdf
OTH, there no spec listed for Choke qualifying - assuming the list number Olie has is 80570. In that case, maybe all he saw was the action of the manifold vacuum on the choke blade itself.
