For the op...
After I completed the following list, my Z's clutch feels great! I only get clutch chatter when going up hill.
Also note, I've never removed the "helper spring" and don't plan to.
1) DOT 4 hydraulic fluid
2) removed clutch line restrictor and replaced w/Dorman brake line union
3) Z speed CSC and SS line
4) Input shaft greeezed with MANLEY Xtreme pressure lube
5) Xedy clutch/PP/single mass flywheel
6) FSM clutch pedal adjustment
7) FSM clutch air bleeding procedure