Hey great video!
A couple observations.
I was struck as well as the porsche hung on the back of the GT flashing his lights as if saying "hey pull over, I want to pass you". This might have been for approaching slower traffic they both were going to navigate, but the lead GT never flashed his lights. Might have also been intimidation factor trying to get the GT driver to loose his concentration. Didn't work.
In the 10 minutes of video, these two cars were the track class act. They sliced and diced through other traffic with superior speed and driving skill. Perhaps it was a mixed class race and there were other similar performance cars on the track that we did not see, but certainly these two drivers/cars are very good.
In the early part of the video the GT seems to have commanding "pull away" power over the porsche. This seems to diminish towards the end, possibly tires giving way. But each time the porsche pulls up to the GT's door to overtake, the GT driver keeps the lead.
Good video, thanks!