Ff
I feel like this one's pretty obvious but
http://www.mangago.me/read-manga/haru_wo_daite_ita/
http://www.mangago.me/read-manga/yatteraneeze/
never read it bec. cant stand tragedy. but its seems pretty amazing
http://www.mangago.me/read-manga/1999_shanghai/
not exactly sure if its the 90's
http://www.mangago.me/read-manga/hero_heel/
fuwa shinri has more then one from the 90's
http://www.mangago.me/read-manga/yasashii_kankei/
same
http://www.mangago.me/read-manga/hana_to_ryuu/
not sure with this one. the art seems old? or may its just the artstyle
http://www.mangago.me/read-manga/ganbare_nakamura_kun/
someone who recommend me a yaoi that was published in the 90's? any type is fine.