Not sure were but I was just reading a post that talked about dented side pipes well here is one way to work the dents out. This was a small ding but this works well on all dents in the headers or pipes. Sometimes a little heat is necessary also to work out the bigger dents when pulling with the puller.
I didn't have to fill any dents or pits in these so I don't have photos but all I do is fill what will not work out with weld, I use my tig welder mig is to messy. I fill the low spot and do the grinding, filing and sanding as in the photos and there all gone. I hope this help and you enjoy.