OK, guys, bike's been doing this since new, but I hadn't thought much about it until I pulled the plugs the other day to see what the color looked like since the cam install and dyno tune. The front one looks pretty good, I think, but take a look at the rear one. I think it is valve guides. What do you guys think?
The bike has just shy of 17,000 miles on it and the plugs have about 1,300. Whenever I would change plugs on this bike, the rear one would always be sooty and a little damp. It's never seemed to affect performance and the bike has never seemed to use oil. When we were in Maggie Valley last fall, Unbalanced (Harry) said he could see a whiff of smoke every once in awhile when I would get on the throttle out of the left pipe (rear). I did not think much about it at the time, but no doubt the two are related. I've not seen any smoke at idle or at start-up and no one else on the rides down there mentioned seeing any smoke out of the bike, so I'm thinkin' it's not toooooooo bad.

If I'd have pulled these suckers after getting back from Maggie Valley last fall, I might have tried to have something done over the winter, but since we are now in the midst of riding season, I plan to keep on running it and keep an eye on both the plugs and the oil usage.
Let me know what you guys think.
FRONT PLUG: