NOOooo! don't drill the air bleed out. First start with cleaning the carb, this is just a measure to ensure it's in good order. Reinstall and read your manual, there will be a base air setting, this will be the carb opening setting, open the barrel to acheive the proper opening distance, now reset you HSN and fire it up, tune for 300 off peak, (use a tach) and now go to idle, use the pinch test to get it close, if it dies when you pinch, close the airbleed down to enrichen the mix and vice versa. Now here's the point, the transition has to be steady throughout the entire range, it should hold a peak rpm, mid rpm and a idle for at least 3-5 minutes, let's face it, when's the last time you flew around on idle? Most air bleeds are limited in tuning, but they are no different than a regular 2 needle setup, you just have a reverse acting adjustment on the idle circuit, instead of fuel, you fine adjust the air supply. I suspect that your too rich on the idle and too lean on the HSN, try leaning the airbleed out and retuning the HSN, the primary barrel gap has to be set correctly in order to achieve proper tunability. Good luck and keep trying to tweak it so it's reliable but smooth in all throttle positions.