probably because the factory R31's turbo was screwed and he put on a cheap and available alternative (if its a straight bolt on, if not then i dont have a clue)
after it stops when i first start the car, it doesnt do it anymore unless i try to use the windscreen dimister. then it comes back for several seconds.
I think its something to do with the vents (when the vents change position
on turbo cars bov's are the first thing cops look for (they dont know what they r for, just know they can defect you for it) so i would put a stock bov on it just incase
or you could just risk it and possibly lose $18 or so