Couple comments on Z's splitting...
I've had the same issue. I had Z-1's, Z-2's, 314-1's (1" ferrule, pre-cats, post cats), 314-2's. (never had the -3's). Maybe 15 of them in total since 1999 when I got my first one. I might have had 5 or 6 split, from normal play, not abuse. Both Z's and 314's...