I just got back from the dealership, with it being a holiday weekend two of the fellows I really wanted to speak with weren't there .... as of right now, my best guess is an issue with the truck's Active Fuel Management System (AFM) .... that's where the truck's computer changes from 8 cylinders to 4 for fuel economy and emissions .... when in 4 cylinder mode it can have a tendency to load the dead cylinders with oil that then doesn't completely burn and creates the carbon deposits .... in our truck's V8, that involves cylinders 1, 4, 6 and 7 .... the spark plug in post one was in cylinder 4 .... I was able to speak with a fellow a good ways up in service who I've known for most of 30 years and have come to trust .... everything is documented about them working on the truck at 61,000 miles at which time they installed the plug shown in the picture above .... he was really interested in seeing the plug.... he's going to get with their warranty folks and see what can be done .... I do have a lifetime warranty on the internal engine parts and it got his attention when I said that I could always wait for the motor to hand grenade and let them drop a new one in .... I figure that is a worst case scenario that they may want to avoid .... I told them I'd check back in the middle of next week ....