Quite a few with thoracic outlet syndrome have had trp inj. -you can do a search on that forum or even the whole site to find posts about it.
http://neurotalk.psychcentral.com/forum24.html
many aren't able to post regularly anymore so a search would be a good way to find the info.
Have you had any "hands on" or manual TrP therapy?
If not I suggest that first to see if they can be resolved without injections.
or possibly acupuncture?
do you have specific little knots that are very sore to pressure ?
where are they located all over or just certain muscles?
PS - I just noticed your siggy- that you have MPS - I was thinking FMS only.
here's one of my threads full of therapy links and more-
http://neurotalk.psychcentral.com/post388-1.html