Usually that type of set-up is connected up top to the anti polution air injection at the exhaust port. In its stock configuration it injects filtered air from the air box to the exhaust ports to help fire off any unburnt mixture thus reducing unburnt hydrcarbons on trailing throttle-making your kwacker more eco friendly. You can (as in the photo) run a breather line from any spot on the crankcase plumb it to the exhaust port anti pollution system and the high velocity in the exh ports creates negative pressure which helps to "unload" some of the pumping loses in the crankcase. And yes theoretically the pistons should rise and fall easier, making your motor happier to produce more hp. If your motor isn't worn out (ie, good ring seal) and of stock cc's the original breather system should be adequate. Big cc motors or motors with cylinder leak down will be the ones that benefit mostly from this type of secondary breather.
Last edited by beenthere; 01-13-2010 at 09:12 AM.