Originally Posted by mhabs
Have the M Performance Exhaust and had zero issues at Laguna at WOT (think the station was between turns 5 and 6), which is probably comparable to Dinan at WOT. Depending on the event, they may have a speed shop set up onsite that rents exhaust muffling pipes that attach to your cans, are bent and point to the inside of the track (they offered these rentals at my event). But cat back cars and some pretty loud stock exhaust cars (including Ferraris, McLarens, Vettes, CTS-V) were totally fine and within the 92 db limit.
I think weather plays a big role. On cloudy days, the meter reads higher. I've seen stock GTR's and Lotus Evora's get black flagged for sound.