Quote: I run Dynomax Ultraflows under the floor with a Magnaflow straight-thru muffler by the gas tank in my E-body, and I don't consider it too quiet, but of course that is a subjective matter. If you look for a recent post by Y07_A66 you will see some posts from me with acoustic sound levels comparing the Ultraflows by themselves versus two mufflers on both sides. The sound plots came from a smartphone app. Adding the second muffler on each side did make a substantial improvement.
