Just an issue I had that, figured I will post the fix since so much threads talk about the problem and there is no real follow up on the fix.

Problem: At WOT throttle clutch got really stiff and pressure bleed off after shifting leaving the clutch pedal close to the floor barely allowing room for clutch disengage/engagement or stuck to the floor not allowing it to disengage it at all. Pressure always slowly came back eventually to clutch pedal till it felt fine.

Fix: Replaced Master cylinder. It was leaking internally

 

I had same problem but ended up being tob

 

yup mine was tob as well

 

I believe you guys are correct. The master cylinder fix allowed pressure to come back after a couple pumps before it would stay soft for hours. Changing TOB next.