I have an '03 with the 5.4. It threw a temp sensor code awhile back. I replaced the sensor and while I was at it I replaced the plugs, coils, thermostat and water pump. After a while it developed a mis (completely dead #4) I replaced the cam pos sens. , replaced the injector and then took it to a dealership; where they did the same things I had already done + checked the coil and injector for ground and power. Still nothing was fixed. I did a compression check and with a leaking o-ring on the comp fitting it showed 120lbs pressure. I've checked every line I can find for vacuum leaks..I'm getting really frustrated with this critter.. any ideas?