Mr. Gambetti want you to take out an old friend: North Korean counterfeiter Kim Young-Guk.
Head over to Mr. Fuk's Rice Box in Alderney. The maître d' will state that Mr. Young-Guk is in a meeting with the manager upstair. After a few seconds, he will pull out a gun and try to shoot Niko. Fight your way to the manager's office (there's a flying rat on the upper level, so letting an RPG off the chain may be a good idea) and threaten him to find out when Young-Guk is. The manager will say that he has already fled through the kitchen. After he exits the kitchen, he will try to escape in a PMP 600. Luckily someone has "conveniently" left a motorcycle for you. Once you kill Young-Guk, the mission is completed.