Hi! Man you have better PC than I will ever have so this is what I did and my GTA IV works 35 FPS with Icenhancer. MY PC:
GF 8800GT 1024mb
Intel Core Duo 3GHZ
I have AMAZING GRPAHIC with 2 mods:
First I installed this graphic mod wichis is in 90% a copy of Icenhancer 1.35
after I installed that graphic update I downloaded this (use only timecyc from this mod!!!!! - not the visual settings):
I uninstalled the GTA 4 ...5 times in a week till I've found this 2 mods which enabled me perfect playing
To put the name of a modding car use program: GTA IV Vehicle Mod Installer
It allows you to instal a car in 2 seconds and it also allows you to restore old cars...you can name here a car you install so you can see this name in a game like BMW, Ferrari...instead of COMPACT, Turismo..ect.
Traffic load works for me so I can't help you. You must open the txt file in that mode and type 1 instead of 0 to make it working.