I do recall that during dyno testing the carb guy at the shop made an alteration to the secondary linkage to make the secondaries come in a little sooner than they did in stock form. He did this to help cover up a lean spot when running at a fast cruise speed. I am going to take a close look at this to see if it might be binding.

Ayuh,..... Like SB said, the throttle cable/ linkage should be adjusted to hold a slight tension, against the idle adjustment screw,......

Open a little is what I was thinking. Since you said someone has messed with it I would look there. I assume it is Holley with mechanical secondaries, if so the link that pulls them open also pushes them closed.

OK, ran it on the hose this morning. Was still sticking without throttle linkage installed, so the problem was with the carb. Pulled it off and examined it closely. Didn't see anything obvious, but I could see a little bit of a carbon line where the secondary plates had been riding in the bore, and it looked like the transfer slot could be getting exposed a little. So I backed off the little limiting screw for the secondary a quarter turn, and I took the return spring one more trip around to give it a little more tension. Cleaned all the carbon off the bore and made sure I couldn't feel a step in the bores. Put the carb back on and checked to make sure there wasn't any interference with the gaskets or the throttle bracket underneath it. When I started it, it still seemed to hang up slightly with no return spring or linkage installed, but once I put my spring and the throttle linkage back on, the problem seems to be solved. Going to water test it this evening to see how it does. Thanks for all the replies!

It shouldn’t need a spring to keep it closed. The cable should be able to close the throttle body. Sounds like something is binding... replacing the baseplate is not out of the question and not that expensive. Just my thoughts.

Cable adjustment.
Disconnect cable from carb. Set idle speed with "stop screw".
Now, adjust cable so that when the throttle lever is back at idle, the cable pushes back a bit against the stop screw.
Then, push the throttle lever wide open. When the lever is at wide open, carb linkage should also be fully open. If not. See if you have stop screws on the helm lever. Or maybe move the cable attachment to a hole closer to the shaft centerline.