I know caffeine potentiates regular NSAIDS by 40%, does it potentiate narcotic gesics too?

Forty percent? Jeez, they didn't teach me that in pharmacy cl! In fact, we found that it appears to potentiate OTC NSAIDS in fewer than forty percent of respondents. When we conducted a controlled study a few years back, we found the difference in response to NSAIDS accompanied by caffiene from that of NSAIDS without caffiene was so small as to be statistically insignificant. So no, I suspect strongly that it does not potentiate controlled substances to a significan percentage either.