I been runnig smooth for a while....After a coil pack was put on about a month ago. Two day's ago engine light came on and it started to run rough. So I pluged in for the codes. miss fire on all pluges.....So I changed them all tonight.......Same...messeage miss fire on pluges. While I was looking or a problem I tested each pack to see if there was a problem. One seemed as though it wasn't affected if I unplugged iot or not. Dash says Electric something. Any thoughts? Has a lot of power