A few tips:

Although I've never done a car rally thru the Gap, since 2000 I've gone 4 to 5 times a year on my motorcycles. I'm sure the car events are different from the motorcycle events as there have been many many killed on bikes there. This is what I've experienced:

The Gap itself has been relatively free from cops. The entrance from the bottom however has been a different story. Usually there are cops sitting on the srtaight-a-way before the Gap actually starts getting twisty. Watch for TVA cops around Fontana. If you ride the Cherohala Skyway be prepared for roadblocks...i.e. insurance and current tag and current driver's license. Also if you ride the Cherohala Skyway and you find yourself with no one around and you decide to put the petal to the metal....DON'T ASSUME YOU'RE ALONE! TN Air Patrol and NC Air Patrol fly helicopters daily over the Skyway, especially when there is a crowd. These guys aren't lazy either...they will time your speed thru certain checkpoints from the air and they will video it and they will send a trooper or deputy to have you pulled over ticketed. I have 2 friends that were ticketed on the Skyway and actually drove back to NC on their court dates to find themselves on video speeding for a judge to see. Like I said though, these have all been motorcycle trips. Basically, obey the traffic laws for the most part and every once and while kick it down and you should be fine....catch yourself running thru the twisties like it's the Indy 500 and you'll probably end up without a license or over a bluff. Just respect this roadway. It is a super fun time but it can get dangerous very quick.