I wouldn't worry about this. My car was over 100 db @ 20' on the dyno, and it passed noise restrictions at HHR
I will be down there for this event, and I encourage the rest of you to join us! HHR is an awesome track, with lots of elevation changes and blind corners. It's a real treat to to drive, and HHR has one of the best clubhouses as well! Relax between sessions on the back porch (where you can see 90% of the track), or cool down inside playing Gran Turismo on the 60" HDTV. Hope to see you there!