I replaced the original Walker SoundFX on '02 Avalanche (5.3L) and I am pleased by the sound of the Flowmaster. It's not necessarily loud, actually very quite until 2k RPM then it becomes noticeable but not too much. Has the typical Flowmaster's rumble from the outside but doesn't scream excessively. When compared to my other vehicle - Tahoe with Magnaflow - I have to say, this one sounds bit more distinctive. Very happy with it. The length is exact match to factory muffler, yet the body is slimmer and clears the frame better.
Sound comparison: youtu.be/2d0oRsqkMSQ