With good Intelligence and Science skill, you can get clue from Myron how to make antidote for Jet. If you tell it to doctor in Vault City and also give him one Jet, he'll produce an antidote you can use to solve Redding drug adiction problem (which lead to Redding epilog where it got under Vault City influence). In Restored game, you can save Sulik's sister. But she's not in Den. One of slaves will told you about a slaver camp south-west from Den. There Sulik's sister is.
So it makes sense that Painless Johnson would seek to reduce the influence of Jet in Redding! Too bad about Vault City though, but it is nice to see that there's other ways to reduce the drug's hold over the town. I was wondering whether Sulik would make any comment on ridding Den of Metzger, but I guess it wouldn't have mattered, really.