If you have ever seen the inside of your intake manifold it is kinda like a filter for oil vapors.. Very hard to describe but the best example is its like a detention pond once the pond fills up then it will spill over a dam into the intake tubes... you could probably put a full bottle of sea foam and it will just sit in the bottom of the main chamber and evaporate. That i know of there isnt any special vacuum line that will bypass that "dam" and go into all cylinders...