Brake Booster Question

[dnoda]

I recently bought a '68 Mustang coupe with a 302, auto trans, power brakes / steering.

According to the previous owner, the brake booster either needs a new check valve replaced altogether. The shop manual I have shows on an auto transmission car, the the check valve has two hoses connected. Of course it doesn't say where they go... obviously one goes to the manifold vacuum port.

Where does this other hose go? It wasn't hooked up to the booster when I bought car -- maybe this is the problem (engine stalls when the booster is hooked up and I press the brake pedal)?

Thanks!