Mustang backfires
I had the same problem which code 0340 came up.I changed the camshaft position sensor,but that didn't change the backfiring.I took of my alternator to have it checked @ an auto part store which they said it was good.The auto part store was wrong my alternator was bad.It made a whining sound off an on which is a sign of the alternator going bad.I changed out my alternator and the backfiring went away.