It can't be the vacuum actuator because it does it with it disconnected.
Remove the check ball and try it again. The vacuum can is holding air and keeping it open. I have ran 3310 and 1850 holleys without the check ball and never had a problem. kwik check on if it is the check ball is remove carb hit the throttle linkage to wot and if it sticks turn it upside down to unseat the ball. If it then closes you found the problem. Then go back to remove the check ball.
It can't be the vacuum actuator because it does it with it disconnected.
Are the secondary butterflies hanging open or closed?
If you have nothing attached to the throttle shaft and it still sticks, I'd say you have a bind in the shaft where it goes through the throttle body. Or the throttle blade is a little off and it's sticking on the side of the bore when closed.
Oky reread the posts and realize it's hanging open. Check the small piece of linkage on the accelerator cable side of the carb, has it been played with or bent, did somebody put a screw in the secondary side were that linkage slides? If thats all good you probablely have a hang-up problem on the throttle body bores where the shaft goes thru. And one more thought does it have the mechanical choke and if so is that closing all the way?
Okay, I found the problem. When I got the rebuild kit it had a different base gasket and not thinking I used that one. The difference was the old one had 4 round holes and the new one had one big square hole. Changed gaskets and no more problem. Thanks to everyone trying to help me. Another lesson learned