I just recently went through this, a friend rode my bike for me a few times while I was overseas. I got back and about shit when I saw all the burnt shoe rubber on my pipes. He said he tried to get it off and had no success (of course spraying it with a water hose won't work)
I tried the oven cleaner gig on cold pipes and hot pipes "nothing"
I tried brasso "nothing"
I tried numerous chemicals "nothing"
only thing that worked for me was to get the pipes very hot and scrub with a soapy wet brillo pad and I mean scrub hard and keep it soapy wet or it will scratch the chrome, use several pads if yours is jacked up as bad as mine.
Use nevr-dull. It's the shiznit. You have to use some elbow grease but it won't scratch chrome. It comes in a silver can and is like cotton with some sort of solvent on it. Tried to load a pic but couldn't from my phone.
I've never used it, but I saw a pipe cleaner in HD store the other day. It id SUPPOSED to work on just this thing. I feel your pain, I've been there. I just wrapped my Thunder Header in the end. No more melted boots...