hello , i have a gtx 560ti , and i run the game on drx11 with 60-90fps , but when i enable the texture pack , the fps is 40-60 and often drops to 20 , why?

because the textures needs a lot of ressources.

because the textures needs a lot of ressources.
RAM specificly

video card ram?

DX9 got updates as well, it's not just the texture pack and textures generally shouldn't drop performance like that on their own.

the thing is , drx 11 doesnt change anything for my performance , but when i disable the textures i get a massive fps increase