Hey guys, I had a separate post that I made talking about a couple of cruisers that are Non-ELS that also have identical ELS-H versions. In order for this to work you have to have ELS installed properly. I use V6 and have had no problems whatsoever. Just make sure to disable ELS for AI in SP mode in your ELS.ini. They won't need it anyway.
Non-ELS Chevy Impala
Non-ELS CVPI
Ok, using these two cars make the CVPI your police and the Impala your police2. I got this idea when Break said he didn't mod his police and police2 with ELS enabled cars, and it helped his stability. These cruisers are not ELS enabled, so you won't have to worry about the extra load on your system when you acquire a lot of back up units. These will be the police vehicles that all the AI drive.
Second thing you want to do is go to C:/GTAIV/Common/Data (or wherever your GTA folder is located). Find the file called cargrp.dat. Scroll down until you see the line that starts with police, police2... Delete the other cars behind police2 so that the line has only police, police2 in it. This will ensure that only those vehicles are driven by police in your game. These will be the units that respond to your back up calls, the Non-ELS modded cars we added in Step #1.
ELS-H CVPI
ELS-H Chevy Impala
Ok, these cars are identical in every way to the Non-ELS cars you added in the first step, except that they are halogen only versions of the vehicles. These two vehicles are going to be the vehicle that the player drives. One goes in the FBI slot, the other should occupy one of the stockades. You'll have to edit the handling.dat and vehicles.dat to make the vehicle you replaced the stockade with handle and act appropriately in the game. Also make sure to edit carcols.dat to change the FBI and whichever stockade you use to be white. Make sure that you enable the halogen only option for these vehicles.
Last thing you want to do is edit the popcycle.dat file and replace every value you see for perccopcars column to a 1. This will reduce the number of modded police vehicles found throughout the city, and as a result lower the polys to make your game run more stable.
For textures, I use LCPD Themed Livery it gives some nice looking textures for the LCPD.
Well there you go, you now have continuity in your livery, none of your cruisers look out of place, ELS or not, and you have the functionality of ELS in the cruisers that you, yourself drive. I haven't had a crash since doing this.