Grand Theft Auto 4 (GTA IV): Game Optimization + Unlock settings

Game performance increases by 5-20pps
You can also put textures on “Hight” on any computer
Copy this file to the root folder of the game (\Games\Rockstar Games\Grand Theft Auto IV).

Grand Theft Auto 4 (GTA IV): Game Optimization + Unlock settings

Or just create in the folder commandline.txt file and write in it
-noprecache
-nomemrestrict
-norestrictions
-availablevidmem 3

List of all commands in the commandline.txt file