Yes and no, I have the backbox with a mix of other bits and bobs including decats and my K2 dropped its baffles very soon after I got it. I also had to get the inlet to the box red hot to bend it to the correct angle to fit it to the car as it was completely wrong, as well as one of the hangers wasn't at the correct angle. I also had to take a hammer to the tips a few months after I got it to stop the inner skin from rattling. I literally had to smash the lip in to get it to roll over more onto the inner skin and bite down to stop it from vibrating.
Now you may think that all the fitment issues may be from a crash damaged Z which is putting the parts out of line, but my car has never been in a prang and the back end is 100% perfect (the front is another story, but thats from my drifting )