Fellow Piriformis Syndrome sufferer here. I've had it for over 5 years. When it was really bad I had to stop all Deadlifting/squatting type activities as well as running. Stretching was bad for me. Long distance hikes were good but short ones bad. I had to get past a certain point for it to start getting therapeutic.
It was (and still is) helpful to sleep with a heating pad. I've got one with a timer so it goes about an hour. If I wake up in the night I'll flip it on for an additional hour. I don't use the pad anymore in the warmer months. Vibro message helps. Anti-inflamatories help a little. Cortisone injections were absolutely worthless for me. Physical Therapists made it worse. Active release was no good.
I'm now at a point where I can run a full sprint and I can squat light. I do overhead squats so it feels like I'm working harder but I'm not using a weight that make my ass scream. Wait, that didn't sound very good... makes my piriformis scream. That sound better.
I sure hope something of that is helpfull. If you find anything that is works, please let me know.