How do de-restrict a CPI gtr 50cc?

I have a CPI gtr 50cc scooter, its a 2007 model, quite fast however, its still restricted, many of my friends have said they got rid of their limiters by putting on a sports exaust because the limiter was in their exaust, however they all have speedfights and so on, i dont want to spend money putting a sports exaust on if the limiter is somewhere else, so can anyone tell me where the restriction is?