As popular as GT500s are I really can't believe that some company hasn't copied them and maybe made the muffler bodies look a little better, but kept the same sound and internal design. Hmmm maybe this is one of those times when I have an idea and a month later someone gets mega rich, and I'm like "Hey that was my idea".
The problem with that is the price. Nobody seems to have managed to design, build, and sell axlebacks for the cost of the GT500s. Most of the muffler deletes cost more!