[Gaz64]

Any form of vacuum can plumbed to all runners is only to supply a more steady vacuum signal for MAF sensors, and for power brakes.
It does nothing for reversion since the takeoff port is insignificant in comparison to the inlet port area.

Some manifolds come with the bottom sealed off with a removable plate, where the runners are connected by a small about 3/16 port.
That volume then becomes a large damper to give steady pulsation-free signal strength to MAFs, etc.

Gary