After 70 hours playtime still far away from classic skin!

[SchumiVettelDE]

Because of display stuttering and input lag I can not get more than1.200.000 points :-) and also not get the classic skin.
I push the buttons but nothing happens especially at speed 50! For me its the best arcade game ever but I do not know what I should do! Do anyone know a way to get a fix for that issue?

My PC:

Intel I7
NVIDEA gtx 670
16GB RAM
Win 8.1 64Bit German