Low D3D and FPS Dirt Rally

[RauloAST]

Hi guys, i have intel i5 4690k, 8gb of corsair pro ram and msi r9 280x twin frozer... the issue i got into is: when i start up Dirt Rally my cpu usage is 50-57% and Gpu D3D 70-90, but after driving 1 track gpu usage gets smaller, and also fps gets smaller, after 2 tracks its about to lag already becuase gpu usage is like 30 and fps 30 and less... when i start to play my average fps is 76 so why does it drop down and doesnt go back up ?

 

[fredfinks]

overheating video card?

 

[RauloAST]

overheating video card?

Thanks for taking your time of reading this.
VRAM Temps never goes over 42c and GPU it self 55c, im using liquid cooling for it.
Will i post some screenshots of temps and usage..
Ou i also have latest drivers, and card isn't overclocked either,