[Shujin]

Nitrogen Bomb seems to not benefit from any power boosts. Things I have tested that leave it entirely untouched:

-Upgrade (Flamethrower) from engineer (says to add 15 power)
-Further Madness
-Ring of Throns
-Blacksmith Upgrade doesn't effect it either
-Sharpen
-weapon sentimentality
-Katana master

Things that DO work are:
-Material Power
-Sharp (The Green Quality text)

I update the list while I try stuff out, but as far as I can tell it only uses the base power of your gun.