Vacuum Question

No adjustments to the carb, other than a slight adjustment to the 2 idle mixture screws - very near to the edelbrock settings. - Timing is set at 15* at 900 RPM, vac disconnected. -- (1) Does all that I've done explain why the stumble went away ? -- (2) Should I put the vacuum tube back onto the ported side of the carb and be considering some changes to the carb instead ? -- The car is a 3,000 lb Street Rod - Stock Convertor - Auto Trans - 3.54 gears. -- Runs fine, as is, up to 80+ MPH - tempted to leave it as is, but don't want to cause other problems.