Bad booster?

Testing w/ a manual hand pump might be inconclusive, at least I recall trying once, couldn't pump a vacuum, yet booster was OK. Once you remove and before you send it off, test it by hand. Connect it to the intake of another vehicle, which known good vacuum. Push in the pedal rod. The output rod should follow your motion. You will hear a hiss as it moves. When you push in the pedal rod, it leaks in air on that side which makes the forward force. When you stop moving, the hiss should stop. Most commonly, the rubber diaphragm fails where the vacuum port connects. Fumes from the engine attack the rubber, and it probably doesn't like the ethanol in today's gas. Happened to me even though I installed a charcoal filter in the vacuum hose. The diaphragm was hard and brittle at the port and cracked. The rest of the rubber was like new.