回复：我是刚来的，都不大懂，所以你们都是专家啦。多谢回复！

You have very strong background but if you have a support letter from gov dept, that would be much better (NIH...). If you cannot get it, try the alternative way. For example, ask a letter from a professor with a title (chairman...) of national professional association ( American heart assciation, American Physiological Society ...), may help you a lot. Try it, you lose nothing. By the way, NIW requires not only the outstanding achievements but also emphasizes an interest of national wide, to fit American needs. In my experience, recommendation letters are the most important factors in the procedures, so take time to prepare well.