Interesting stuff. I just got back from Laguna Seca where they have a 92db limit for track days. They have a sound booth setup on drivers right between turns 5-6 where you have an uphill straight, it's about 50ft from the track.
I usually am at wot shifting from 3-4 just as I pass the booth. Well, I got the meatball flag and was told my exhaust was measured at 98.2dbs. Unabombers data showed 98 db with a similar setup. Unfortunately, I had to lift there the rest of the day and held my lap times around 1:50.
on my '03 I have vf34, borla headers, vishnu up, helix catless d/p and a borla hush exhuast.
fwiw, the setup sounds awesome at wot, especially ehcoing off the cement k-walls going up the Rayhal straight.