Problem solved. Ted was right. It ended up having nothing to do with the carbs, slider, throttle cable, fuel pumps, needle choice, or throttle or air screws. The problem is that when we first started looking at things yesterday we had removed the fuel pump bracket. When we put the bolts back in, they weren’t tightened completely and it was letting in air behind the carb, which would explain why we had the problem when trying three separate carbs. We tightened everything back up the way it should be and the issue went away. Everything looks good now. Thanks for all the feedback and tips.