NO one way valve with aftermarket, vent to atmosphere(through tanks) systems, as std they used a closed crank vent system, whereby oil fumes/pressure was ingested, good for some things not power though.
This one way was fitted into the centre of the plenum cover, the large hexagonal bit with a pipe coming off it, this was so that the boost wouldn't be lost as otherwise it would go out the same place and be lost.
tabetha