I don't have the cultural issues you do, but I can understand your feelings about your parents' inability to discuss your adoption openly with you.
I'm also an adoptee (though quite a few years older

), and my parents too find it difficult to discuss our adoption (my brother and me). I remember being young and folks asking where I got my brown eyes and both of us our height (we're both many inches taller than our parents!), and her making quips about vitamins, or talking about my dad's father having brown eyes. From reading here, I can imagine other issues at play that are more innocent, but to me, I guess I always thought she was embarrassed that we were adopted.
When my brother's birthfamily located him a few months ago while I was in the midst of my own search, my mom became very upset, and told me that she was our only mom, and she didn't want someone taking us away from her. Remember at the time we were 42 and 39, and have kids of our own! I can't imagine the reaction if we had been 20 years younger!
So, I do understand how this can be very hard, for you and for them. All I can suggest is that you be true to your own needs to explore your cultural identity and roots, while trying to be sensitive to whatever insecurities and fears your parents have. For me that has meant multiple conversations, emails, letters, assuring and reassuring her that I will always love her, that she is a great mom, that I'm not trying to replace her, that I adore her, and will do whatever I can to help her believe that, and feel safer about this. I also asked her if it would make her feel better if I didn't discuss it with her, or I told her everything I found. She opted to know, but that's hard too - I still feel reluctant to share too much because I feel I'm hurting her - a delicate balance to find.
This is not easy, and in my worse moments it feels a little unfair that I'm agonizing over the feelings of my birthmom and my mom, and that neither appears to be terribly concerned by my own needs, fears, feelings (yuck - self-pity feels blah!

). But, after venting to forum buddies, I'm better able to look at it that my Mom is important to me, I love her and I don't want cause her any unnecessary pain -- then I can get a grip again and try to be as understanding and reassuring as I can.
I feel for you. It is definitely a hard place to be in, but I think it helps to talk out the feelings here.
Good luck! Let us know how things are going for you, ok?