I believe I have a vacuum problem but not quite sure. Car will be operating fine but when I apply my brakes to stop there is no booster assist. And if I go to turn the ignition off it continues to run and I have to manually kill the engine by depressing the stop lever in engine compartment. Let the car sit for a brief period and upon restarting it will operate normally. I can drive the car when it is acting up and after a few miles it will start behaving normally. Am I on the right track? If not what is it?