Hi Matt, sounds like slave cylinder to me. Any chance you can get the car to a local garage so you can check the clutch line and slave cylinder?
Let me know if you need parts, both in stock and ready to ship. Hope you sort this out ASAP!
Gearknobs: http://www.350z-uk.com/topic/99093-torqen-350z-370z-blox-racing-limited-series-6-speed-shift-knobs
Slam panel: http://www.mishimoto.co.uk/mishimoto-nissan-350z-air-diversion-plate-03.html
As you know, we're working on a real Grade 5 titanium version, should have them here July / August.
Little update on this:
AAM started working on building the first two kits, one for the 350z HR and the other for 370z. As soon as they land here, we'll start working on them and post details and progress here.
Looking forward to receive them in the next few weeks!