It's not clear what the terms of your transaction were, or why the car isn't registered to you, and you don't say what it is that makes you think there's a GPS tracking devce on the car. However, if the car is not yours (i.e. you don't have title), the owner can do what they want with it.
In every state I know about the dealer MUST give you a signed copy of the K at the time of sale. If you can somehow prove they did not do this, you can probably get out of the deal. I have no idea how you can prove it. There may be other infractions present here and TX has a strong consumer protection act (one of the few things W did not gut while he was there) so, get hold of a consumer protection atty in your neck of the woods and see what you can do. Look here for someone competent: http://www.naca.net