Found a quote:
"Engine sound has been improved from Gran Turismo 5 Prologue, but surprisingly, the game does not run at 60 frames per second at all times. In certain conditions, Yamauchi admitted, when heavy technical effects pile up on one another the frame rate will drop a bit. For example, in a race when there are fifteen cars kicking up dust in front of the player, the game may experience some skipping. That sounds like a fairly common condition for players to be in, however, so I’m curious to see how players take to this unsatisfactory blip in what seems to be an otherwise flawlessly realistic racing game."
CS races are fucked!