Are you saying the Engine vacuum? I dont get what you've have been asking that your vacuum are weak. For any reason, if vacuum are weak then the problem are vacuum leak.

On older carbureted engines, vacuum is needed to pull fuel into the engine. Vacuum siphons fuel through the idle, main metering and power circuits. An engine with a vacuum leak, will likely be an engine that suffers from the symptoms of lean carburetion such as lean misfire, hesitation, stalling and rough idle. Sometimes that symptoms can also be caused by a clogged catalytic converter or other exhaust restriction, a leaky EGR valve or valve timing problems (all of which reduce intake vacuum). This will apply to fuel injected engine also. Check all your hoses for small crack you might have to change if brittle, clean all the oropice w/ needle maybe they are clogged,(male oropice are small piece of metal where you connect all your vacuum hose.

Important thing to keep in mind about vacuum leaks is that they have the most noticeable effect at idle.