I think he's talking about the dark dots on the tarmac.
And generally you shouldn't ask yourself "which file in the F1 folder...", many people waste time tweakin the game this way and then complain to "CrapMasters" when something bugs.
In this case, there's simply a graphic option to switch.
Don't know which one, but I remember I saw them once while I was running test benchmarks.
You may turn all graphic options to off, and try them one by one to see which one creates these dots.
I would start with skidmarks & cloth