I have it working on my build. One of my main problems is texture loss, would have been great if it had a bar representing the allocated memory for this script, because it isn't my PC or graphics card causing the texture loss. Vehicle de-spawning seems to be a thing for me as well as emergency lights being disabled off-screen.
For anyone who has issues with this GTR's livery, I give credit to cats9142430 on the Reddit chat for Essential Mods. I will use police4 as an example.
* General rule of thumb, make copies of the original files. I cannot stress this enough, always make duplicates before you mess with them incase of error or rollback to. *
Open OpenIV.
Right-click the YTD file associated with this car (your vehicles.rpf file path).
Export the following files:
gtr_sign1.dds
gtr_sign2.dds
gtr_sign3.dds
Make a copy/duplicate of these 3 original files.
Save the copy of the 3 original files separate as to not confuse yourself later on, whether rename them or put in a secondary folder.
Open the files in Paint.net, Photoshop, etc.
Make the liveries transparent, meaning hide/remove/delete the layer with the sheriff and/or police livery, then overwrite the files.
Go back to OpenIV and replace those 3 files in the YTD file, then save.
Next time you run GTAV, it should appear without the liveries. It if helps any, I'm using the unmarked w/o spotlights. I'm able to change the paint color without issues, I used Simple Trainer.
Youtube is your friend. "lspdfr install vehicle els". It should walk you through on how to create the mod vehicle folder (YFT/YTD), edit vehicles.meta, handling.meta, install ELS plugin (XML).