Get RC5 then in the engine section of the ini file all you should use these settings but change the resolution to your screen resolution
[ENGINE]
ForceDisplaySize=true
ForceDisplayRefreshRate=false
ForceAnisotropicFiltering=false
MaxAnisotropy=8
AntialiasingSampleCount=4
DisplayRefreshRateHz=60
DisplayWidth=1280
DisplayHeight=1024ReflectionsForceHighPrecision=true
ReflectionsExtremePrecision=false
Edit: Just a screenshot here to show the new effects brought in by this.
Normal GTA IV:

GTA IV ENB style:
