NOISE->>2006 with CAT-Bypass vs stock 2007

Last week I met another Captain, his is a stock 2007.

Mine is a 2006 with stock pipes and Cat-Bypass.

When I put the CAT-Bypass on it was at least 3 times as noisy. Not overly. But I have to admit that side by side mine didn't sound much louder. Mine should bark more!

Now I wonder why....

1- Does the 2007 have different pipes?
2- Can the tune make that much difference (No recall on his, mine has the stock tune)
3- Anything else we've missed?

Just the Cat-Bypass was much of an improvement, enough for me. The TORS would be too much. My air filter is stock.

Now this stock 2007 Classic is almost as loud as mine. Which means that the stock 2007 is much louder than the stock 2006. Any idea why?