Exhaust pipe...

Them pipes sure can cook anything they touch. I had a small spot from the wife's boot that came off with oven cleaner too.
 
Not an issue since I switched to Satintunes many years ago my pipes are cool enough to touch after just a minute or so.
 
Looks like you have so much dirt and grime on your pipe it will peel off and leave a shiny spot.
Mike
 
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