Find your engine.ini file. Mine is at

C:\Users\lolsomedude77\AppData\Local\Insurgency\Saved\Config\WindowsClient

Paste the following lines in

[TextureStreaming]
BoostPlayerTextures=1.0
AllowStreamingLightmaps=False
r.Streaming.DropMips=0
r.Streaming.LimitPoolSizeToVRAM=0
r.Streaming.MipBias=0
r.Streaming.UseAllMips=1
r.Streaming.UseMaterialData=1
r.Streaming.UseNewMetrics=1
r.Streaming.UsePerTextureBias=1
And done.

Basically the game runs terribly because of the streaming process. Once I disabled lightmap streaming and didn't limit the streaming memory pool to my VRAM, the game boosted my performance significantly.