The cam in my cutlass is big enough to annoy me at stoplights with a pedal that sinks to the floor. I'd say it does it about 70% of the time and varies with the weather(?). It does it more with the engine warm as well so I'm guessing it's not enough vacuum. Will a can help with the stoplight problem?
Nope, that's probably your master cylinder or air in the system. Lack of vacuum will give you a high hard pedal.