Yes, you should most certainly have vacuum at the source/intake manifold.
You should be able the test the effect of the brake booster with an alternate vacuum source - if you use a vacuum pump you should be able to draw vacuum on the booster and it should hold for hours.
The vacuum booster is very good at holding vacuum - eg. if you get in the car many hours after it last ran, and press the brake without starting the engine, you can do that 3 to 4 times before the pedal gets hard, which is when the vacuum stored in the booster is depleted.