As you can see this is often a hard thing to diagnose. The first thing I would do is get some approved cleaner from your local parts store then clean the mass airflow sensor and replace the spark plugs and also get some injector cleaner. If thiat does not help you will need to bring the vehicle to a shop that has a smoke machine so they can force smoke into the system and visually inspect for leaks. Let me know if you have questions, thanks.
P0300 Multiple Cylinder Misfire Detected