The engine knows because the straighter the line from the carb to the valve the better. None are perfect, but a individual runner intake (Hilborn, Weber, etc), and the true tunnel ram are very colse. Think of a crossram and standard dual plane intake. The runners are nice and long, but the fuel and air need to make an immediate turn. Air isn't happy doing this, and fuel is even less happy. It tends to cling to the walls of the ports. There also is issues with fuel puddling below the carbs. The engine is just an air pump. Easier air in and easier air out, the better in most applications.