I have a 2000 4.6 with over 200000 miles. I am the 2nd owner of this vehicle, got it in 2002 with 52000 miles. It has been well maintained. I have changed out the plugs and coil packs several times over the years. I am getting random missfire codes at the same time. I have changed the coil packs and plugs on each coded cylinder . Still have a bad missfire! Sometimes it will only be a missfire on #8. I know the plug is good that connects to the coil pack on #8. When it does give a random missfire code it is #3 and #8 mostly coded but sometimes it will be other cylinders? I was driving this vehicle almost everyday and it was running fine then started missing really bad and throwing codes.