I was thinking about this a bit more...

If there was an issue with either the master or slave cylinders, wouldn't I have clutch issues all of the time? My clutch issues ONLY happen when it is above 80 degrees. I have clean clutch fluid (just changed it), however it is DOT3.
Would DOT4 fluid make a difference?

 

The fact that this occurs as temps increase actually supports the possibility that the is hydraulicly related. Remember, fluid viscocity is affected by temperature. So to is its ability to pass air bubbles through the system. When you say that you cleaned the fluid, did you flush the system? Or did you just pull the fluid out of the reservoir? If you didn't fully flush the system then you could be seeing air discplace the fluid in the lines or in the slave or master cylinder. I suggest using Motul RBF600 fluid as it has a much higher boiling temp than the OE fluid. It's worth a shot...Let me know if you have any further questions.

 

The problem with higher than DOT 4 is, the higher the dry boiling point the faster the fluild absorbs water from humidity in air. Oem uses DOT3 because it can usually last 2-3 years whereas some exotics are designed to be replaced after every race or every month depending on local rain conditions.

Any brake fluid that has ever boiled is worthless as the chemistry has changed and it begins to absorb moisture at a faster and faster rate.

 

How can moisture be an issue in a sealed system? (not intended as a smart-a$$ question)

 

Boiling of the fluid causes it to chemically break-down and as such leads it to respond as it would if moisture were introduced to the system.