08 1800N. I noticed the last few hundred miles of so, more vibration than normal. Also, my mpg dropped slightly. Vibration not in the tires as it goes away with clutch pulled in and coasting. I pulled the plugs and this is what they look like after 8k miles or so. I went ahead and swapped them cause I had a new set laying around and all the vibration is gone and she's feeling peppy and responsive again. What causes the plugs to look so bad so quickly? 16k on the bike. Valves checked at 8k. Cobra powrpro, intake, exhaust. Thank u.