system 'adds' the airflow of both sides. Where the pipes split from there to the seperate MAS/filters, the flow of air is evenly split such that the MAS is always measuring exactly half of the intake air and therefore maintains a smooth and consistent A/F ratio. The 'other' system out there splits the intake tracts which generates all kinds of problems. The idle air control valve only pulls from the driver's side intake, but it feeds both sides of the engine. In the 'other' configuration it cannot properly compensate for the fact that the MAS is reading one side of the engine's comsumption, PLUS idle air for both sides. This throws the air metering way off which is why a 'low load drivability kit' even exists.
