it's been my experience that true piriformis syndrome is rare.

The suggestions below are all fine, but if you combine them, you're throwing everything but the kitchen sink at the patient. I'd recommed you attempt to find which treatment group (i.e. specific, directional exercise such a McKenzie; lumbar manipulation, lumbar stabilization or possible traction). Then, make one treatment type the focus of subsequent sessions. If you throw all of these treatment variables at the patient, all at once, you really make the picture far more muddy than it needs to be.

First question: Did you do a formal McKenzie repeated movements exam at initial exam?