I'm pretty sure if I remember correctly that's the only vacume line envolved on the entire set up. Now correct me if I'm wrong, wouldn't the bov only cause a problem under boost and not idle. I didn't think there was enough boost created until around 4k for that thing to even open. I think everything else that is modified is either Pcv related or coolant related.
BOVs can definitely cause problems at idle and definitely make the car just stall if there is not enough pressure on the piston.