Master Cylinder ?
i had the same problems. i would bleed the system out and see if that cures it. when i took mine apart the fluid looked like black paint in the slave cyl. i havent had any issues since i put in the newer style slave, a new master, and a new clutch. i figured id do it all in one shot since it was apart.
start with flushing the system out. i bet the pedal will feel much better.

