When strong vacuum is created, to the contrary, there also is strong pressure. Cylinder pipes are connected with Bypass Pipe to reduce pressure as minimum as possible. Rhythm of "Pressure" and "Vacuum" inside manifold is controlled.
Besides, number of bypass pipe and positions are designed to optimize for each engine characteristics. It enables to reduce pressure without change of vacuum. Therefore, there is no drop of torque. The engine will have Inertia Exhaust Gas Efficiency (Efficiency to increase horsepower of NA engine) and flat torque characteristics, which enables easy drivability.