[danw]

I have a Wilwood slave cylinder for my clutch, and the first "incident" with the newly-purchased Cobra was losing the clutch pedal completely as I was blissfully cruising down the street. As you can find via various threads on this site and others, this particular slave cylinder has an end cap that is prone to unscrewing itself under normal operating conditions. When this occurs, you lose clutch pedal, first gradually then abruptly (and probably also the return spring out of the slave cylinder).

If yours is the same design and the cap has started to loosen, that would explain the change in the "feel" of the clutch. I used Loctite 242 thread locker when I put mine back together and it hasn't budged since.