Yeah, that's what I'd bet on. Plus you can see how its really rounded/oddly ... Your one from cyl 3 looks 'better' in terms of the gap ... they just needed to be replaced!! Did you use motorcraft plugs? Holy crap, I just read that those were the factory plugs ... no wonder they look like butt! I bet its running wayyyyy better.
Oops I didn't even see that ... That's some iron knee .. lol Did you try resetting the comp? I don't know if that would matter but it wouldn't hurt. Are you sure you gapped the new ones right? I don't even know what the gap is supposed to be ...
One time I got a misfire after plug change. It was because I had forgotten to plug one of the COPs back in Another possibility is that since you did not grease the spring ends with dielectric grease one or more may not be seating properly on the top of the plug. And yeah, reset the PCM.
i am detailing my engine bay for a show on friday so ill take a look and see if i missed one or see if it wasnt clipped in all the way