[Flat6pac]

The hose from the oil tank to the airbox, under the air filter is the supply of fumes off the tank. Any moisture and oil fumes that are in the tank will vent to the airbox. There is a hose off the bottom of the airbox that directs the oil off the top of the engine.
If you want to change the system, use the 78 and later oil vent hoses and the black boot that cross from the airflow sensor to the throttle body. The fumes go directly into the throttle body.
2 atm on a 2.7 is too little overall pressure cold or above idle. I would change the sending unit after making sure that the old sending unit is actually a 0 to 10 atm
Bruce