Engine light came own couple weeks back said misfire on cylinder 6 park the car up that night next day engine light came off and it wasn't misfiring anymore now recently engine light came on and misfiring so I change my spark plugs and put in a new cool pack on cylinder 6 plug and out everything back on car still feels like it's misfiring but engine light wasn't on so today it was misfiring and engine light came on read the code p0300 it's telling me random misfire or mass air flow sensor or large vacuum leak etc what should I or do I need to do to fix this problem please help me thanks g35 forum

 

Check for "uncommanded air" past the MAFs (mass airflow sensors) aka an air leak between the MAFs and the throttle bodys (loose clamps or holes/rips in the hoses/snorkles).