GTA IV gets FPS Lag when I get into pursuits all the time, And its annoying!! I usually run at 25-30 FPS and i'm happy with that and when I get into a pursuit.. FPS Lag not low FPS. Anybody know a fix? 

It's probably all the AI's data being loaded up at once, the pursuits on any scripts always suck up resources because of how badly optimized the GTA IV port is for pc

It's probably all the AI's data being loaded up at once, the pursuits on any scripts always suck up resources because of how badly optimized the GTA IV port is for pc

Well do you know a fix for the lag?

First off, is it a legal copy of the game? 

Secondly, post your computer specs! 

There is no universal fix for GTA IV, just a bunch of them and you can hope one of them works... To circumvent a less powerful computer, and maybe get the game up and running, create a txt file called “commandline.txt” (without quotes) in your main GTA IV installation directory. Insert the following lines:

-renderquality 0 -shadowdensity 0 -texturequality 0 -viewdistance 0 -detailquality 0 -novblank -norestrictions -width 320 -height 240 -safemode -windowed -availablevidmem 2 -percentvidmem 100 -minspecaudio -novsync -renderquality 0 -frameLimit 0 -nomemrestrict

This will force the game to minimum settings. If it runs lag-free, consider changing the file to: 

-novblank -norestrictions -availablevidmem 2 -percentvidmem 100 -frameLimit 0 -nomemrestrict

Also, always make sure to run as administrator: 

You do this by going to the GTA IV folder, right click on GTAIV.exe -> Properties -> Compatibility and select 'Run this program as administrator'. Do the same exact thing to the LaunchGTAIV.exe file.