Create a text document named commandline.txt in your root folder and add these lines to fix performance issues and remove restrictions:
To mod version 1.2.0.43, users require updated versions of core tools: gta 4 1.2.0.43 mods
Due to music licensing, Rockstar removed dozens of songs from Vladivostok FM, The Beat, and Liberty Rock Radio in 1.2.0.43. Create a text document named commandline