The disks are different for sure, because somebody tried to fit a set of gti disks to his gtir and they wouldnt fit. The calipers must be the same but their brackets are different and that why their P/N arent the same i suppose..
The reason i am asking is that i ve traced a brand new set of rear gti calipers, but they ll do either way because i just want to take their shiny pistons to replace mine. There is always a chance that i m sooo unlucky that even the gti/gtir pistons are different, but lets hope not :-D !