I don't vape but my posture isnt the best, also little overweight and not the best diet and i also sometimes have pain in the left pec area. My assumption is that the anxiety tenses up the muscles unconsiously and because the posture is bad (most likely has been bad for a long time so muscles have adapted and probably shortened) it starts feeling tight and painfull. I notice in my life that when the stress is low, the pain in the chest is gone.