I ran EBC Reds on my modified R32 and warped the stock disks as the reds ran bloody hot on track, and the std disks couldn't dissipate the heat fast enough.. new drilled and grooved disks and a new set of reds later, they were superb

Also use Ferodo DS2500's on my track toy, but I'm not sure they make a set for the S4??
Cheers,
goose