I just received my new Corsa Sport mufflers from AM, and as soon as I picked up one of the mufflers I heard what sounded like a little ball rolling around inside the chamber. Is this enough to be worried about? My old Roush mufflers made a lot of noise, both when on the car and when picked up, though those sounded more there was sand moving around in the chamber. They would rattle at a certain RPM, so that's what I'm mainly concerned about with the new mufflers. I figured this wouldn't be an issue with high quality mufflers like Corsa, so anyone know if it's really an issue?