Never tried any earlier patches but the performance on my PC got better with patch 184.108.40.206.
But that'd mean you'd have to uninstall Icenhancer and shit so I'd try some other stuff first. How are the graphical settings in your menu? Have you maxed everything out? Might be worth a try to put the night-shadows off and set the rest a little lower.
Gta 4 has the memory capacity 'meter' which tells you how much of the maximum memory (of your gfx card) you're using. I know it's tempting to try to maximize that but I have it set on about 0.6/1.0gb.