with the Pyke Syndicate and speak to the Pyke in their district who's sitting at a table near the card room.
He explains that someone is circulating fake credits in a bid to undermine the gang and he wants you to find out who it is. The intel gives you a search area in the market, but it isn't at all clear how you're supposed to determine which trader is doling out the fake cash. Here I'll explain where to find the market trader in question and complete the quest.
, but if not, you can always sneak into the district through the vent to the right of the soup kitchen entrance—just get Nix to hit the switch and open the vent. , which is in the restricted area. I recommend hopping up onto the landing pad via the platforms to its right, then using Nix to hit the switch and stop the fans so you can crawl through. Then all you need to do is climb down the ladder into the room and investigate the box at the back., which will mean more rep with either.