can anyone help with this fault i read the codes

1) P0300 - INTERMITTANT MISFIRE
2) P0303- INTERMITANT MISFIRE ON CYLINDER 3

I HAVE ALREADY CHANGED

1) 4 XPLUGS (NO DIFFERENCE)
2) 4 XCOIL PACKS (NO DIFFERENCE)
3) ALSO FOUND THAT SOMEONE HAD TAMPERED WITH THE AIRFLOW MASS METER SO REPLACED THE MASS METER AND THE PLUG HOUSING CONNECTING TO THE MASS METER. ( BETTER BUT STILL NOT RIGHT AND STILL GETTING ERROR CODES).

ANY SUGGESTIONS