ok had my code pulled at autozone and it came up as a po304. missfire in cylinder 4 what can i do to fix this. i have nothing major done to my car. i have a blitz racing spec cat back and just install an egt gauge. i took it to the dealer once and i think they just reset it.they said they had to send the ecm to subaru
light came back on few days later so i took it in and had the code pulled. is this something to worry about?