IIRC the exhaust extractor PCV system is there to ensure the crank case remains at negative pressures during WOT conditions. This is something that isn't really useful for us (unless you're running a Diesel engine) as the stock PCV system should be pulling a vacuum if it is connected to the intake manifold post throttle.
On a Diesel engine it may well be of use as Diesels do not run an intake vacuum, and therefore can only plumb the PCV system into the air intake, which will not pull much of a vacuum at all.
I have an exhaust extractor valve, a catch can and a PCV valve that I may well put to use on the Focus Diesel
