GTA IV has nightmarish mouse smoothing by default. In the repack, open FusionFix.ini (located in update folder) and set:
: Mr.Goldberg and Christsnatcher; Rockstar Social Club is no longer required to run the game. Grand Theft Auto IV - -DODI Repack-
Expect 3/70 detections (Usually "Packed.Win32" or "HackTool"). This is the crack. The actual game assets are clean. GTA IV has nightmarish mouse smoothing by default