I love GTA IV modding, but it's almost impossible.. It's enough with 2-3 mods to totally ruin GTA IV, it stops loading objects/textures after few minutes of gameplay. I've tried low-poly cars (essential packs), putting only one, removing parts of maps (I removed 70% of map, it gave me +5-10 minutes of gameplay), and so on..
I have 12GB of DDR3 ram and 2GB of vram (HD6950), I'm playing GTA in 720p, everything low (getting almost 100fps), yet it's impossible, have to restart game every 10 minutes.. I've read many guides, calculated my own commandline, browsed google for months.. nothing. Almost everyone else seem to have find an solution, not me.. I don't recall this happening in early modding (I believe I had a pirated copy back then, not steam version). Some asi unlocker mod was fine to run everything I wanted, even with 9600GT and 4GB of ram. I updated drivers recently, game version - 188.8.131.52..