Was on an old tired engine when i first got the car 4 years ago....had a standard breather on and use to blow the dipstick out...put a breather on it and it stopped doin it lol. God knows why but it smoked like hell on overrun when i vented to atmosphere....put it back into the metering unit and it didn't??!! Didn't bother to find out why as i didn't really see any massive advantage in venting to atmosphere.....the engine and turbo was tired tbh...that was 2 engines ago mind lol.