Ive got no muffler on mine with a dual 3 inch pipes coming out before the passenger side tire. As far as sound its fairly loud when accelerating, and extremeley loud when floored. It has a nice tone and very deep rumble when accelerating,and a few people have told me that it has the same sound as a nascar when floored, just not as loud. My friend has a flowmaster and his truck no longer sounds loud to me at all if that helps. Also i havent experienced any popping noises at all when letting off the gas. Hope this helps.