crank breather filter?

[vwwvgolf]

ive read good and bad things about these, just wondering if anyone here has anything to say about them.

ive read theyre good as they dont return hot oily air back into the intake, but they have something to do with pressure in the crank case and balancing it out. although this is only necessary on some engines??

obviously i would then bloke off the hole where it goes into the airbox. ( if i ran one)
what are peoples views??

[itavaltalainen]

what engine have you got?

the larger ones have a unit fitted already. the amount of oil going to intake from there is not an awful lot.

[vwwvgolf]

for a abf,
just trying to get it as efficient as possible lol