I have pretty much the same system specs as he does, and GTA IV runs fine. All the videos on YouTube feature horribly low spec machines bossing out GTA IV with no problems. It seems the better your machine is, the worse the game runs, truly anti-PC. True definition of a console port.
That's one of the worst posts I've read. My 2500k @ 4.6ghz and 6950 run GTA IV maxed out with an enb and high definition car mods at 1080p just fine. As I've told you before your game runs fine because you play at 1440x900.