I went to get a dual exhaust installed at a local muffler shop, however the owner did not want to install the system. This is because he previously installed a dual exhaust for a customer who was not happy with the changes in sound when afm kicked in. He said there was a muffler on the market that was made to deal with this problem but he was not sure of the brand or model number. Is there anyone who has heard of this?

I am only looking for a muffler and not the entire exhaust system as I was hoping to have the shop make the remaining setup.