Try using the align_epi_anat.py script to do this for you.

align_epi_anat.py -anat spgr_T1+orig -epi epi.ppm002+orig -epi_base 0 -tlrc_apar spgr_T1_at+tlrc -anat2epi -suffix _al2anat -volreg off -child_epi stats.ppm002+orig

This command will align the original epi dataset to the anatomical dataset and then compute the combined transformation for the epi to tlrc space. The statistical dataset will be transformed using the same transformation matrix.

One reason adwarp may not give good results is if the epi dataset is oblique. You can check if the dataset is oblique with 3dinfo. Either use the align_epi_anat.py script to handle this or deoblique the data with "3dWarp -deoblique".