I have had the same problems-
change your brake fluid and your clutch fluid while you are on. I've had my brake and clutch pedals go to the floor (not at the same time!) due to old fluid, boiling.
On the 350, I run standard discs, ebc yellow, ATE super blue fluid and some cooling ducts to cool the front brakes. This setup works for me on track.
P.S I saw you and your car at Cadwell on Sunday, I was in the orange R1 kit car. I might have some on track footage of you, I'll Check.