In my case I don't have any sound problem, but I see like a slow frame per second rate at some points of the intro, for example the first pit lane image, when the driver is going to mount on the Ferrari, a few seconds before..
I don't know if you're meaning that lag, but yeah I see it after the August update.
All the rest of my game and things on my Playstation 3 are completely right. I use a Western Digital 250 GBs HDD and I don't think it's due to the hardware or corrupt install file of GT5P, it's just about the GT TV update into the new menu & pay things, maybe the intro doesn't run smoother as before in the new GT TV (it happens on GT TV but also when you see the intro normally).