1st Check for air leaks in the Booster, Inlet Manifold and Carby, also check the Distibutor that the vacuum advance is working. Check for any broken gaskets or hoses that lead from the carby or Inlet manifold... When all are fixed then you can tune it properly.
See the only leak your allowed to have is through the Butterfly valve and any air coming from anwhere else is bad news, it means your car will run out of tune.