Many believe a q-jet is not adjustable and has to be run as it came from the factory. To make matters worse, many old q-jets have been abused, thrown around, dropped, messed with, etc... and things get out of adjustment. Look at the rebuild instructions and go through all of the adjustments shown. Many adjustments require bending things. Do em all. Pay particular attention to the setting of the air valve over the secondaries. Too loose and you get a bog. Too tight and performance suffers.
Soak in good clean carb cleaner. The kind that comes in a can big that you can submerge the carb in. If you done have or want to invest in a can at least find a shop that will clean it for you.
Make sure the plugs under the float bowl are sealed good. I like to epoxy them to be safe but a foam plug that just fills up the area under the bowl plugs is available but is only a temporary fix. Make sure secondary butterflies seal good when closed. If not usually causes a rough idle and inability to adjust mixture properly with idle mixture screws.
