Your two cents wanted on the condition of my spark plugs.

[lostranger2026]

I just replaced the sparks in my in my (new to me) 1999 Ford Ranger. I don't know when these got last changed, car has 170k on it, engine rebuilt at 110k, but my oh my. I don't think I ever saw sparks worn down this much.
So what I noticed is that left and right are worn quite differently and I'm scratching my head on what could have caused this uneven wear. The plugs are in the order of the cylinders, with the number being the firing order from the coil pack.The entire right bank looks a lot more sooty, they are Motorcraft 32FM's. Could these have been original to the car?
The distributor cables had dielectric grease on the metal inside instead of the plastic housing, that definitely didn't help either.

At the end of the day the entire lot was replaced with Autolite APP104's, NGK cables + coilpack. It sounded much better but I suspect I'm still missing quite a bit of oomph.

 

[alwaysFlOoReD]

It may be because its a waste spark system. The current goes in one direction on one half and the other on the other half. So you need dual precious metal plugs. IE: double platinum.

 

[SenorNoob]

The 4.0 originally spec-ed 2 different plugs for that reason. I find it simpler to just use the doubles too.