[CBRBob]

Put the hose from the crankcase vent to the airbox back on. You want negative pressure in the engine as much as possible. You read about how 'improved crankcase design drops pumping losses'. All that means is they found a better way for the air to move from the underside of one piston to the other easier. If you make a vacuum in the crancase, there is less air for the bottom of the piston to push against, hence, less power lost, and no oil drool on the outside of the engine.

One trick you will find in dragracing is that they have several vacuum pumps on the crankcase to gain power. Keeping the hose to the airbox helps, there is nothing to be gained by removing it.

Leave the pair on a stock muffled bike. There is no performance gain by removing the pair. The only benefit is if you put an aftermarket exhaust on you will hear the popping on closed throttle decel, disabling it takes away the popping. Also if you have the bike dyno-tuned, it needs to be disabled.