Yes a vacuum leak would cause what is happening,just left you a reply on your other post,might add that the vacuum tree that all the lines feed to on the intake manifold can create problems in this area as well. I don't think it could cause one this big though. There is a ten mm bolt that holds the part to the intake, take the vacuum tree out and you will find a flat shaped o ring, in my car it had just about completly disintergrated. I replaced it and found a little power and better gas mileage.
With a leak big enough do cause your problems, I would think that you would have an idel problem. Does the car idel OK? Is there a change in idel when you put your foot down on the brake pedel? Try taking a vacuum gauge and hooking up and let us know how many inches of mercury she's pulling.
Poolman