Just kearned that J-1 visa holder is free for OASDI and medicare for 2 years but I had the dudections 4 months after I came. I started my job in Aug. 2008 and got the deduction since Jan, 2009. Is it possible?

To get FICA taxes back file Form 843. It is filed separately. Your U.S. Tax Return: Social Security and Medicare (FICA) Taxes for Non-resident Exempt Individual (http://taxipay.blogspot.com/2008/03/non-resident-exempt-individual-social.html)