Point in BOVs or recircs is to keep the turbos from being surged with pressure when you close off the throttle bodies... i.e. when you close them off, the air BEHIND the turbo has no where to go, and there is still air coming INTO the turbos... so the BOVs blow off the excess intake pressure coming to the turbos to slow them down slightly so they don't receive a back surge of pressure... I "believe" that is correct... but I didn't engineer the damn things. Someone correct me if I'm wrong.