Jake, I had no idea you had a 911. Cool car.
A 911 (not sure which model) showed up to the 13 Hour Enduro at VIR back in October. Ran flawlessly the whole time. It wasn't stinking fast, but it wasn't slow either -- 2:23 was its best time I think which is approaching mid-pack in S (after a year of working on me and my car, another ITS dinosaur, I'm at 2:22). You need to run 2:18 to 2:19 to crack the top 5 in a decent ITS field and 2:15 to win. 8 seconds sounds like a lot but at VIR, a 3.27 mile course, it's not as much as you would think.
Since the car was in enduro trim and was probably not being pushed to the max like in a sprint race, it certainly would seem capable of 2:20s which would be back of the front pack at VIR and a decent time.
Encourgaging, but as Jake says, it would be an expensive car to run.