I was surfing through the games files to find something interesting when I came across the files of Luis' clothes. I noticed that it only had a diffuse texture, but I swear I was once playing as Luis, he was wearing his jacket and I noticed some specular highlight with that shiny sh*t and stuff.
I don't know how R* does this, it's probably like the vehicle system. They store the reflective data in a .dat file. But that's impossible since there's no way it's going to have some shiny detail without its specular or a normal map.
I was also trying to screw with some speculars to make all the sh*t in the game too shiny just 'cause. But if someone could enlighten me on this, I would appreciate it.
EDIT: HOLY sh*t! I found that the normals and specs are actually located inside the model files.