My muffler started making a buzzing sound slowly over time and now happens at higher RPMs. I took it to a shop and they said i have a small leak at the donut gasket and at the head. I ran up on some debri on the highway and nailed the header so I already purchased a new one. Could this cause the buzzing sound out of the back?? I can't find a leak in the back either but it could be small....The muffler is a borla universal and is about a year old. Could the muffler be blown out?? If I need to replace it I want to take it to a custom exhaust shop to get some mandrel bent tubing.

Any input is appreciated

thanks