I went for a test ride to test out the Krankvent system.
I got the Krankvent from here http://www.krankvent.com/
(3/8 inch metric fitting) after getting involved in another thread (Crankcase Breather Valve and Marbelized Breather Hose). The idea behind this Krankvent is to let the pressure in the crankcase out but don't let the air in thus continuously maintaining a vacuum after the engine is running. By maintaing the vacuum, the pistons don't have to work hard since it is not trying to overcome the pressure in the crankcase during the down stroke phase. The linked web site also claims that due to increased differential pressure, the pistons rings will be better sealed and no oil blow by.
My initial reaction is very positive. The engine seems to rev up much easier than before. The web site claims a few HP increase but w/o a dyno, it is hard to prove or disapprove. Theoretically, the product design makes sense. The only issue remains is how long this will last. The product is guaranteed forever to the original owner so I am optimistic at this point.
Installation is very easy. I just cut the crankcase breather hose in half and inserted the Krankvent. The only issue with the product is that the direction of the flow is not marked so I had to blow w/ my mouth (as the instruction recommends) to find out the direction of the flow.
It's kind of expansive but I think it was worth it.