I bought this muffler to replace the Flow Master 40 series. The Flow Master 40 series is a great muffler but the only thing wrong with it for me was a thud at highway cruising Sounds great under acceleration but not at cruising That's why I bought this Borla Flow Master muffler and it's simple and a little louder than stock and smooth you can feel the pedal increase response. I put this muffler on a 2013 Chevy Silverado 4x4 Cab 5.3 engine. If you like vibration and volume, choose Flow Master. If you want a smooth and near-factory sound, choose this Borla. I make Flow Master no blame because they make a great product it's just a matter of preference.