For Original GTA IV mods, despite the patch, you need to follow this procedure:
1. Put in your retail disk
2. Beat the first mission and save the game
4. Hotswap with the modded disk
5. Clear your system cache
6. Play the mods
If you don’t do this, you’ll most likely freeze on the loading screen of the game.
I will get my own video of this recorded soon, but for now here’s a video I found on youtube.