I've only ever tried two types of pads with my R brakes, EBC Greenstuff and Mintex M1144.
I don't rate the EBC greens at all.......very good out of the box but once taken through a number of heat cycles they lose their edge and become very inconsistant.
Mintex M1144 are more expensive, I find they wear quicker than the EBC's and dust like crazy, however I find them to be a very strong street/fast road/track pad for the K11. I hammered them as hard as I could at Brands to see what they were capable of and they didn't once let me down.
There's quite a few options for the GTI-R calipers, so I'm sure others have used some different pads.