I\\'m at a loss 2000 excursion v10

I think I\\'m posting in the right area. But I have a 2000 excursion v10 with the 3 different cylinder misfires. OK I\\'ve done all of the normal changing of the plugs, coils, and checked the wire harnesses. I\\'m getting power to the plugs by using the light tester on coil and plugs. The number 1-4-&9 cylinders are misfireing. And #9 is carbon coated after a few days of driving. There is no engine noise that would be a problem and the truck has to be totally warmed up before it starts shuttering around 30-50 mph when at low rpm\\'s. I\\'m at a loss and am thanking anyone in advance that has any input that may help. Thank you.