Thanks guys for the reply

I have been doing yoga 2-4 times a week for the last 8 months. I went to see Yamuna Zake (look her up on Internet) in New York who works with people with chronic pain and she endorses body rolling for TOS also. She told me to be careful with down-dogs in yoga. Somebody mentioned up-dogs and as you said anything with strain on neck as risky poses as well.
I have not found a direct link in yoga and flare ups yet (although somedays after yoga I have a few bad days but on other days, yoga improves my pain for a few days). So maybe I need to be watchful and make note which poses led to flare ups the next day.
If you follow the concept of Myofascial Release, it tells us that chronic pain in any part of the body leads to distortion or contortions of the whole connective tissue that envelops our body and that leads to misalignment of the body which puts further strain on the area that is causing pain. Because connective (or myofascia) is pulling it in one direction or the other. PLUS, we tend not to exercise our body because we are in pain or fear of pain or just depressed which further tightens the connective tissue and a vicious cycle ensues. That is where in my opinion yoga becomes very important. Strengthing and stretching back muscles, hamstrings (b/c inflexible hamstrings and low and upper back pain are directly linked) and shoulder opening exercises in yoga are very helpful for TOS. I do agree that down dogs or ups dogs or neck straining exercises should be avoided).
I strongly recommend going to a class as that really increases motivation and improves our desire to help our bodies. DVDs are ok but no substitute for a class.
Hoping everyone's quality of life improves.

Khan