Did this exact dumb a$$ thing Saturday and got my boot rubber melted onto the pipe of my brand new SG. Used some of my daughters fingernail polish and a cotton ball. Rubber came right off!
i figured a way how to remove all kinds of melted crap off exhaust. get a mini torch like this heat up the crap you want to remove. if you pay close attention you will see the rubber or what ever you melted on there crystallize.
that's what i call it,then take OOOO steel wool to it. i have done this countless times. i have found no chemical that works better than this.
Stupid me, melted part of my boot on exhaust. I tried glue remover, goo gone and WD40.
Easy way is to use a single edge razor blade at a low angle, like paralell with the pipe. Then use chrome polish: eagle one wadding polish is good stuff...