you could use the oil filler cap - some engines have a firetrap and a crankase breather built into this

or you could make your own crancase breather - some competition engines add extra ones or enlarge existing ones anyway (this is often high up- on the rocker cover)

the crankcase should be vented - a small k&n type filter is often used (noxious fumes can get into the passenger air intake though) or a catchtank and a breather "exhaust" running to the outside of the car

with the crankcase vented to air the other (intake) end can be blocked - probably best to get someone who knows what they are doing to check it

sucking the boost hose on a turbo engine is a bad sign - it should be under pressure ("pushed out"- not "sucked in" )