I see what you meant. I think the cyl temp difference is inherent to the engine itself. Ford designed a tune to correct it. I think their tune shows they were favoring the cyl's they knew were hotter.
Injectors can cause a cyl difference. But I don't think that is a constant that can be attributed to any of this. It could take out one engine, but can't see it being the problem with all of them. Coolant flow, intake design, header design, etc. Something that is the same with all of them. I haven't seen any corrections for PW on the injectors yet, but by looking at the plugs 6 looked like it was more than 8. I only did the driver bank though. But I think you hit on a problem that's in my head. No injector variance, just plug in the value for "X" injector, and watch the AFR. Now to me if 6 looked colder than 8, why the hell is 8 blowing up. Will take another look tomorrow. Having trouble getting a tune to load in a 2011 here. but when I do, off to the dyno to check the plugs with a canned tune.