hey i've been downloading and adding multiplue police vehicles to the lspdfr files (open iv and ELS file in gta5 main directory) but have had trouble spawning other cars. i'be already added all the cars that fit police, fbi, sahp and lssa but i can't spawn all the vehicles i have. whenever i go to the console and look for police 9 or fbi 3 it won't come up. i know i used to be able to do it but i can't figure it out now. any tutorials or tips that would help?

If you installed the addon cars (e.g. police8) correctly, you can just type "SpawnAndWarp police8" into the RPH console. Even if it doesn't add a prompt for that exact car, you should be able to spawn it regardless. Just hit enter.