MNSmith - I thought this would require a lot more explanation than I can offer so I was hoping an expert might jump in. About your question as to a long straight pipe and no muffler I used to see this years ago on school buses w/ inline sixes and they sounded great. It wasn't too loud however or uncomfortable. So I guess that works OK too but I believe the length of the pipe more or less acts somewhat like a muffler. But yes I do think it's apples and oranges on a high HP engine vs an old straight six.
I don't pretend to understand all of this and it's why I suggest we ask the experts at Gibson or Flowmaster or others. I'm sure they can explain it all properly in terms most could understand.
I hope this string stays alive for a while as it seems to be of interest to many.

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Dave
Engine & Driveline Moderator

If you can't make seventy by an easy road, don't go. ~~ Mark Twain