Those of us that drive Seca regularly will tell you that it's not always consistent with regard to getting meatballed for sound. Especially with regard to the roving person who is supposedly taking readings anywhere on the track. dB limit is usually 92, although I have also seen 90.
When I've driven (HPDE with SpeedVentures, NCRC, and Coastal Driving School/PCA) I have concentrated solely on the stationary sensor trackside on the uphill straight from T5 to T6 (on driver's right). In my stock '09 ACR, I sometimes time my 3-4 shift to coincide with the sensor. Kinda slow shift it. Or you can stay in 4th through T5 and downshift once past the sensor. And you don't need to completely lift; just stay out of WOT. In traffic, I make my passes on that straight full bore in 3rd and don't worry about it: with more than one car in the space they can't assign a dB value to anyone. I've posted a video here ("Seca with telemetry" or something like that) that shows the various ways I drive that section. Honestly, half the time there's traffic around and sound becomes a moot point.
I think that it's wise to reduce your loudness between T5 and T6 during the first sessions. My impression is that the sound check vigilance is most strict early in the day, when they want to identify the "problem" cars right away. Drivers are given a chance to correct their setup, but this applies mostly to guys that have rear exhausts to which they can add a bent tip(s) or traps. A side exhaust car is problematic whenever there's a dB meter around. Anyway, during the last sessions of the day (when I'm really trying to put together consistent, better lap times) I have sometimes driven T5 - T6 at WOT... and I have not been flagged yet, knock on wood.
If you require 100% balls-to-the-wall for the entire course length, every lap, all day, then the sound restrictions will probably prevent you from enjoying Seca. If you're trying to reach for that 1:33, you may have a problem.
On the other hand, if you come out to enjoy a fantastic road course that's loaded with content for your ACR... and you're not a lap timer *****... you should definitely make the trip. In fact, since it's a long haul for you, why not sample all the NorCal courses and add Sears Point (Infineon) and Thunderhill to your itinerary?
If you do decide to come out, PM me and I can help you get in touch with local support for your track days.
Rich
PS You're always allowed "sound check" laps, too: you can go ahead and drive two laps as a test and come back in to see where you're at... so you will not be summarily kicked out after one 93 dB reading.