The pressure plate has no springs. The boxster has a dual mass flywheel made by Luk. Link for info
http://luktest1.ina.com/content/en/products/dampers/zms_sv/zms_lv/zms_lv.jsp
I suspect mine is fuched as it rattles once the engine has warmed up, and goes away on engagement of the clutch... It sounds like ball bearing rattleing.