I bought this muffler to replace a 40 series Flow Master. The Flow Master 40 series is a great muffler, but the only thing wrong with it is that it makes a dull sound at highway cruising speeds. Sounds good when accelerating but not at cruising speed. So I bought this Borla muffler. It's not harsh like the Flow Master, but you don't feel the vibrations in the cockpit like the Flow Master, and it's easy and a little louder than the original and smooth, you can feel the increase in pedal response. I put this muffler on a 2013 Chevy Silverado 4x4 5.3 double cab engine. If you like vibration and volume, choose Flow Master. If you want a smooth and factory-like sound, choose this Borla. I don't blame Flow for making a great product, it's just a matter of preference.