Yeah that's a problem. Like was said, I'd try and get it set up to have the throttle fully closed @ idle on the outside carbs and idle off the center. You can't do that if they are hanging up before they close. Looks like they're are alot of springs and wires in there to try and get it to come down, that can present it's own problems like stiff throttle or foot fatigue cruising on the highway. Do you know what cam is installed in the engine? Your low vacuum is probably b/c you can't cut the airflow through the carbs. It looks like you need longer arms on the carbs to clear the manifold or correct the geometry, at least at the center carb.