whats up with power brakes

Should be a 1/4" diameter manifold vacuum port and line supplying constant vacuum to the booster and a check valve usually on the booster. A small supply line will create the same inch pounds of vacuum in a chamber so large but it would take a minute or so. Then you could use up the vacuum very fast.
Two 1/9" lines do not equal one 1/4" line either. It takes four of 1/8" to equal the volume of one 1/4". Hope this helps