[Eljaro]

I would take the valve cover off and look a the valves and the rockers. If the leakdown test is ok but the compression is low you may have those valves not set right.
When you check compression you should have the carbs throttle plates wide open, otherwise you will not draw enough air into the cylinders.
You can also be having a bad seated intake gasket and the engine is drawing air through there.
You could also have you linkage not set right. Check that all carbs have the idle position set by the linkage and not by the individual stop on each carb.