after a spark plug change i gotten a code p0193. at times car starts and dies. it will take 3-5 for it to fully start. at random occasions on a stop car rpm drops and almost dies. code states its fuel rail pressure sensor high input. where to start? where to check? not to familiar where the pressure sensor is at. want to make sure its the pressure sensor is the problem before buying one. 06 v6 stang here