If lugging at a reduced RPM..... you can get a little harmonics thing going on in the 8220 and the 8400.....($150 ish)


7400....no issue as the muffler is still under the hood  ($12.50 @ napa)


I did the 7400 because I was tired of looking at the stack.....and if/when it's on the Gen Set.....I have a stove pipe I put on and stick it out the door of the shop....keeps the fumes out.