Hell. You state posterior left pelvis tilt? I assume you mean some form of pelvis dysfunction. 2nd you state having tightness of Hamstrings, Gastrocnemius, Piriformis and Sciatic symptoms. Well actually the tightness you feel os the muscle could well be as well a Sciatic symptom and the ankle as well. So you could well be right to think that all the symptoms are an expression of the same problem.
You say you can handle the pelvis tilt, I say you don't No way that you can have a mis alignment of the pelvis complex without affecting other parts of your body (e.g. high toned piriformis). A high toned Piriformis can potantially obstruct the Sciatic nerve. A pelvis mis alignment can affected the Lumbar spine.
What surprises me is that you name all these different muscles by name and even a pelvis tilt. This means that you are under the care of a therapist, or you are yourself one.
So sort 1st you pelvis out and see what is going to happen.
Good luck