hi mate, I had similar problems with my white 33.
I drive my 33 aggressively up on twisty roads and frequently needed to double clutch on corners while driving up hill.
My problems started soon after changing the wheels to 17"x7. The first valeo disk I changed was worn out a couple of months after the installation. The clutch bearing was split in two as well which is probably what ended the life of the clutch itself so soon.
After that I changed the disk and plate to OMP. I had many problems with that setup as well.
Apart from the vibration when the car started to run and the squeeky noise, the OMP clutch was excellent when cold. Then it just started to spin endlessly.
I contacted OMP dealer and he said that because its a drop clutch ( 6 ply ) I had to have a fast return of the oil from the secondary clutch pump otherwise with high revs the disk would become hot before hitting the flywheel !
I soon after removed the OMP disk but kept the plate and used a valeo disk again as I couldnt find anything else to fit.
That setup worked well enough until I did the engine upgrade.
Now I have the standard kit again but I know it wont last long ... I can smell it
Luckily I was able to swap a flywheen of the subaru with a custom made racing clutch disk and bearing with Andrius Klevas ( the guy who put the subaru engine into his 33 ).
Hopefully that will solve my problems.
I recommend you change your disk again as it could be a faulty disk to begin with, but also check the surface of your flywheel. If you run your car with a red hot clutch for a long time, your flywheel may need surface skimming.
Its a shame they dont make propper clutch disks for these cars