My EMG to diagnose TOS was done on both sides, with the needle being inserted into the space between C7 and T1 (the C8 nerve root). It's a bit painful, but not unmanageably so. You will be sore afterwards.

I don't think EMG's are done on the pec minors. They simply deaden the pec minors, and if it gives you relief - then they might consider a pec minor dis-insertion (clipping the muscle where it attaches at the highest point).

Hope this helps - good luck!
Anne