Between 1993 - 1999 BMW recommends ATF in there manual transmissions, that are in the M3's.  I use Lubro moly gear oil.  I have used both the MTLl and MT-90.  I have been the happiest with the Lubro moly.  Even though BMW recommends ATF in some  of there  manual transmissions, I will not use ATF in mine.  It's your chioce.  MT-90 is a bit thicker than the MTL.