It will never be 100% again but that's a classic seal it up, hook it to an air compressor on one end and heat the spot cherry red with oxy/acetylene or MAPP torch and see if you can work it out. Your ultra shady looking muffler shop guys might be willing to help pop it out. Midas and those won't be of much help.
Here is a video
I learned how to do this years ago playing with all of my little 2 strokes. I've also used this method to fix a few gas tanks, just instead of using compressed air you use compressed nitrogen or argon, and at your own risk I shall state.
After working out the dent, you'll need to fine grit sand and lightly polish the pipe to look as close to factory as you can get. One thing to note is there will still be ripples in the metal. Don't try to sand or polish them away until the pipe is perfectly smooth. The metal is so thin you can sand all the way through or so close that it will crack later.
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