I had huge problems with this on my t56 in my 98ss...especially after going to long tubes. It was commonly thought that the heat from the exhaust was boiling the clutch fluid and caused the slave to not get any fluid. I wrapped my headers, insulted the fluid line, did the master drill mod (not an issue on new masters) then even changed the master and slave cylinder. I had this issue with a 100% new clutch. There is no way it was brake dust alone causing this problem. I dont have a manual trans, but you might want to take a look at the routing of the clutch fluid line. Id bet its still near the stock exhaust.
I never had problems until I went to long tube headers though. After changing fluid upon fluid, modding parts and replacing everything. I gave up and went with a th350 anyways. Part of the reason I stayed away from stick this time. Its a huge problem throughout the lsx community.
New dog with the same problems.