I can't speak to the mufflers you ask about. But the more metal *pipe length* and the thinker the metal walls.. the quieter it'll be.
To do mine all over again. I'd run a 2.5" mandrel smooth bent pipe from the cat to a Y. Then have 2.5" smooth bent pipes go over the axle and out behind each tire.
I sorta have this now except I have a magnaflow muffler and the last 2ft of each tail pipe is thick wall regular exhaust pipe steel. It's a little too quiet until the rpms get up to and past 2500. Still sounds decent.. just a little too quiet at lower rpms IMO.
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