Empty the tube beneath the air filter.
The engine has a system to pick up the blow-by air from the valvecover and feed it back to the intake so it can be burned. Also, it gives a slight vacuum in the crankcase, which helps the crankcase sealings seal and keeping the piston rings tight at high rpm.
The problem is that there is oil droplets and water vapour being sucked up too, but that should be caught in the clear tube.
If the air pressure in the crankcase is too high, more gas will blow by by the end of the compression stroke, when the piston and rings decellerate and pressure will rise further. Also, if too much hot gas or oil droplets are entering the combustion, it will be bad for the combustion process.