Well, a quick look at the few Google hits seems to suggest it is being used as a sort of slang word for 'testicle' [more offensive but colloquial words: bollock, ball]; and in particular, the use of 'left gazorch' ---- 'a pain in the left g.' --- could equally well be 'pain in the butt / arse / neck', but there aren't many things in the human body that come in left/right pairs :-)

Also note the Google hit relating to loudspeakers: 'more gazorch in the bass' --- to my way of thinking, this means 'more oomph / more power / more BALLS!'

In your context, it seems to me it is being used to mean something that is very visceral, deeply-rooted in the most important part of the [male] human body... (open discussion of this in another forum, please!)