I bought 100 Taiyo Yuden DVD+R 8X T02 discs. I did test burns at 8X and 12X on the top 2 discs, the bottom 2 discs, and a disc in the middle. They all have a PIF cluster at the 2.3 GB mark. I assume this is nothing to worry about? Here's one scan:
That looks fine. I wouldn't worry about that one bit.