It has a Rochester Type BV single barrel carb.

I have just acquired this car and have been trying to get it to run correctly. I have set the timing, rebuilt the carb, stopped some leaks, etc.... It starts great now and does not flood the intake with mass amounts of fuel..... However, when rapping up the engine I get small and quick mini backfires at the highest RPM.... what is causing this? Also, explain the complete function of the choke vacuum unloader control.

Thanks, Bob