Regardless of installation method, you need to do the following:
To use on any car, edit the vehicles.meta it is defined in, and replace this line with;
<audioNameHash>st29b18cfnf</audioNameHash>

Install this first.
- https://www.gta5-mods.com/vehicles/f-f-mitsubishi-eclipse-engine-sound-add-on-fivem-sound