[Kenth]

The little screw under the metal plate on the airhorn is used for off-idle calibration. If open it adds air to the main circuit on 1970-74 Pontiac Q-jets.
Most if not all hesitation driving is due to lean carburetor calibration.
You may first try to set the off-idle screw closed lightly seated to make off-idle somewhat richer.
This may help some, but in these units the idle tubes are really too small for todays fuel, so i recommend pulling the tubes and enlarge the openings from .029" to at least .033" and at the same time open the idle down channels from .046" to .052" to cure the off-idle issues.
Also, with this re-calibration you will find the factory ignition settings working properly.