What we’ve seen on the VT1 platform is that at WOT, everything vents through the breather tube and not the PCV valve. Vacuum provided by the pre-compressor intake tube airflow is insufficient. Higher pressure through a single small orifice causes more oil to be produced, along with there being no baffle mechanism on the underside of the valve cover which would eliminate splashing oil from hitting the outlet.
Since the Gamma (G4FJ) engine has an abnormally high amount of blow-by (from poor rings, higher boost pressures & easy break-ins), some of us deemed it better to not feed the hot oily air back into the pre-compressor air stream. This coats everything all the way through the charge system to the intake manifold runners with octane-lowering oil, which raises IATs and increases risk of detonation.
We chose to not only vent both the PCV and breather sides, but added a third outlet using a vented oil cap. Overall performance increased and oil emissions actually substantially decreased.
A vacuum pump evacuation assist method was brought up, but the cost and complexity (not to mention weight gain) for minimal performance gain over just venting nipped it in the bud.
The PCV system is an archaic, outdated mechanism that is in sore need for a revised model, particularly for performance cars.
Getting to the Theta-II engine on our VNs, from what has been reported and from what I’ve seen personally, much less oil is coming through the breather tube due to better ring sealing. I’m keeping mine as is for now, but once boost pressures start going up, I’ll be checking the breather tube much more often.
At the first hint of accumulated oil, triple venting will be done. I’m not recommending it officially, but just know it is effective, does produce a slight performance benefit and produces far less hydrocarbon deposits on associated engine internals.
Evacuation tubes can be routed out of the engine bay and attached to the exhaust system for a quasi-vacuum assist, or just dumped under the car. If you don’t want to mess with your pollution control system for legality purposes, you can get around that by implementing the vented oil cap.
YMMV.