After receiving my car and checking out those wires I mentioned earlier, I found out that it was just a poor RGB footwell DIY job. The suspicious looking black box was both the RGB controller and bluetooth receiver, or that's what it seemed like. After that, I opened the sunglasses holder by the sunroof controls and found a very suspicious looking black cylinder. See the pics below. The only thing that I can say about it was that "PG25" is engraved into the metal right next to the yellow tape. Since I have no clue what it is, I'm afraid that if I touch it the wrong way, it might electrocute me. Again, if you all can give me some ideas as to what this might be, I would greatly appreciate it.

 

Just a smart-*** guess: a breathalyzer?

Look under the dash when you have time and see what that gizmo might attach to.

 

You know what, that is a very good guess. When I looked into the trunk, I found two different pictures of the previous owner and both of them are taken next to this car and a cop giving a thumbs up. The cop looks like he can be the guy's dad so I wouldn't be surprised if you are right.