Blanking off the bov, or even adding a ATMO one will no longer make the system "recirc", thus create idle drop and even stalling - my old R32 had it blanked off thus no return pipe into the intake where the AFM could read what was going on.
remove one link in the system = drama.
You can remove and block them/run ATMO's when you have a chipped ECU, thus telling the AFM what to do