Poor brakes at low RPM

[John]

My main concern right now is getting the brakes improved. If indeed the vacuum has always been low (when previous owner first built the motor-which I am trying to find out) then I can focus on getting a vacuum pump or hydroboost. However, if indeed there is a leak or some other mechanical issue, I’d rather resolve that issue and not put an expensive bandaid on the problem. Other than a leak at the carb or manifold (I check hoses and no leaks), what are some other possibilities?

What is the best way to identify leaks at the carb ? and intake? I don’t want to start ripping things off.