I haven't had a chance to snoop around other Triglides to see if they are exhibiting the same thing as my dads 09 and my former 10 did. Both or our Triglides where tuned on the dyno and running a richer than the lean 14.6 and sometimes higher AFR Harley Davidson delivers them at. I started noticing the powder coat lightening or burning off around the spark plug area including down some on the fins. I'm not sure if this is due to running 8-12 hour days on the freeway at speeds of 75 mph + during the the hot months of summer, or something else. I'm thinking its just plane not getting enough air flow across the rear cylinder while riding at those speeds.