Capt Slow, sorry you won't be able to make it. I was looking forward to seeing you there. Have fun test-n-tune-ing the auto-xer.
I have never seen or heard of anyone having problems from the cops related to ThunderDrift. The only thing I've heard about is a general rule about T-Hill: the road out to it has a 55mph limit, and the cops can be very strict about enforcing that limit. So, drive 55. I think they patrol more on big HPDE days, since that's when you get rich guys with expensive sports cars who are convinced their last name is "Andretti" on their first track day.
ThunderDrift is a great event. I have also not seen much hooliganism from people going to/from the event. It's an established event and does not attract a lot of spectators. So the people who go to it care about it and don't want it to develop a bad reputation and get ruined. Most people are driving below the speed limit down I-5.
For me, my car passed smog, has all the registration and such, and is perfectly legal. I also know the law that a cop can't legally search my car without probable cause or consent.