I'VE BEEN FIGHTING THIS SUBARU FOR 40K MILES FOR INTERMITENT P0304 MISFIRE ON CYL #4 AND IT FINALLY DIED. COULD HEAR LEAKING EXHAUST VALVE WHEN IT CAME IN TODAY. EASY WAY TO DIAGNOSE THESE MISFIRES IS TO PULL EXHAUST Y PIPE OFF AND LOOK INTO CYLINDER HEAD. YOU... Login to read more.