I have a 01 heritage the only mods are a 2 into 1 thunder header and a stage 1 air cleaner. It also has about 13,000 miles on it. My problem is I can ride all day at 55 or 60 mph with no problems. I can also run at 70 mph for 20 or 30 miles again no problem. But when I run 70 mph for 45 min. to 1 hour I start to notice a little more vibratin in the handle bars and a slight lack of power. If I let the bike set for about 15 minutes it runs fine again. So do you guys have any idea of what could be wrong? Thanks for you help.