So I've had a lot of problems with adding/replacing cars and other vehicles because if I put the file in to the original .rpf which the read me points to the game starts updating and replaces the modified .rpf. Also when I use OpenIVs mods folder it doesn't do anything I also might be using OpenIV mods folder improperly. I have also tried GTA 5 Mod Manager which I also might be using improperly.