Routing the pair valve hose (the one coming from the airbox) to the breather on the engine is an old drag racing trick, and yes, it is something that can free up 1-3 rear wheel hp. What you are doing is pulling air from the crankcase to create a vacuum - this reduces the engine's pumping pressure in the cases. It is an easy and cheap mod - you just have to remember to run a stronger hose than the stock one - which can collapse under the vacuum created. Old school dragracers used to weld tubes into the header collectors at a 45 degree angle and put a one way valve on it; then they would run hoses up to the breathers on the valve covers - this would create the vacuum in the bottom end and free up some hp. It has nothing to do with oil foaming . . .