Have you installed a new gameconfig for GTA version 1604.1? In my experience, replacing base vehicles (police 1 2 3 FBI etc) with els vehicles adds extra lag and crashes. I have about 30 els add-on vehicles and I only replace the game vehicles with non els vehicles.
Stop the ped
Ultimate backup
Traffic policer
Police smart radio
Search warrant
These are essential for me
Callouts are more about personal preference
If your PC van handle it, these are also good.
Clear the way
Spotlight
Lspdfr comes alive