Crank case vent
When excess blow-by is present, air can go backwards into the TB. If you just gotta do it, put some breathers on it. If you leave the PCV operative, it will cause a small vacuum leak that will eventually be compensated by O2 readings. Or you could disable the PCV system. The PCV system is normaly better for purging vapors, but people with forced induction usually have to run breathers because of the extra volume. Maybe you need to, as well.






