Got around to putting new plugs in my L today. The drivers side 2 rear ones are rusted as you can see in the pics below. Also the rear on the pass side had like carbon build up really bad on one side. Truck idles a lot better now ill see if it still misses at WOT tonight if i get any races lined up.

 

How do the ends look? Kinda hard to tell from the pictures.

I'm guessing you had a little water down there. Also, are you sure those Coilpacks do not have corrosion in them?

 

the tips are brown on all of them except the pass front 2 the pass back on has like a build up on the side of it. The coilpacks on the to with water damage had a orange color from the rust but the metal inside them looked fne. But where could that water come from i dont ever wash the engine and the truck rarely gets rained on.

 

If you did any work on the injectors/fuel rail,its possible some gas seeped into the plug ports.It happened to me.When I removed the coil pack and blew out the port w/ compressed air,orange dust flew up from 2-3 plugs.I freaked out at first,but remembered when I changed out injectors some gas spilled and obviously got past the rubber coil pack seal.

Just a thought

 

No injector work has been done but the fuel solenoid for my NX kit is located right beside the rear plug. Might need to check it for a leak or bad line conection