Yup. The rattle is par for the course with these platforms. An upgraded ZSpeed HD CSC would be difficult, if not impossible, to tell without dropping the tranny. The Z1 would be easy, get under the car and see if has the elimination kit on the outside of the tranny. If not then it's not there.
Check the link for pictures of the installed elimination kit.
https://www.z1motorsports.com/z1-pro...it-p-7340.html