Porshe cayenne pcv valve / porshe Random misfire / fault code P0300

Crankcase ventilation system
In an internal combustion engine, a crankcase ventilation system removes unwanted gases from the crankcase. The system usually consists of a tube, a one-way valve and a vacuum source. The unwanted gases, called "blow-by", are gases from the combustion chamber which have leaked and pass through the piston rings.
And when there are leaks withing this vacuum, random misfore could occur...