ProVent is a filter system employed to scrub the oil from the air circulating from the crankcase to the intercooler. It just decreases the load of engine mist on the intercooler maintaining the efficiency of the charge air system. Called a Mann+Hummel Oil Separator for Closed and Open Crankcase Ventilation.
Sydney Filter Services P/L; Unit 19/70 Holbeche Rd; Arndell Pk NSW 2148 ph 029672-7008. (Australian agents)
They are very helpful.
Many have added this to their systems - a search in this site would yield a fair bit of info on some of the options considered. A lot of Nissans are wearing them too.
You could also search under DarbyWalters over on LOST.
If I may suggest a couple of other things you may already be aware of - * check the MAF for cleanliness and use MAF cleaner to clean it and don't touch the filament nor scrub it. on't use harsh chemicals like carby cleaner or brake cleaner for cleaning this.
* check that your boost sensor is clean - use the same cleaner I mentioned above. That is well documented around the traps as well.