Influencing People

Influencing People is a side quest

Detailed walkthrough
This quest is automatically activated after the completion of All My Friends Have Off Switches, and tasks the Courier to upgrade the functions of all of The Sink's personalities. The player character can collect these upgrades in any order, but the quest will not be completed until all have been installed and interacted with. Upgrades need to be accessed by speaking to the personalities in The Sink.

The holotapes (or terminal entries) for these upgrades can be found at the following locations:
 * Big MT west tunnel: The holotape for the LAER Mod - Auxiliary Recharger Chip is located in a series of rooms containing several Protectron Mk3's and The Custodian. It sits on a shelf in the second large room, in an alcove. It's leaning up against the duffle bag.
 * Construction site: The Sink Upgrade: Water Production holotape is located in the far west of the site, with a skeleton next to a bucket loader.
 * Little Yangtze: The Book Chute Upgrade: Mulching holotape is inside the watchtower, propped up against a coffeemaker.
 * Saturnite alloy research facility: The Light Switch 02 Upgrade: "Mood Lights" holotape is standing in a cabinet in the large factory room, across from the South entrance.
 * Securitron de-construction plant: The Muggy Upgrade: Parts Production holotape is held by 010011110110111001100101, on the second floor of the facility.
 * Signal Hills transmitter: The holotape enabling the Sink CIU to sell the LAER Mod - Prismatic Lens is located on the roof of the transmitter office, along with a note and some equipment from Elijah. It is easiest to walk up the outcrop next to the office and jump down (watch out for glitches in the hill; the Courier could end up inside it). The Auto-Doc Upgrade: Hair Styling Enhancements holotape is located inside the office, on a desk immediately to the right.
 * The Cuckoo's Nest: The Sink Project: Toaster holotape is located to the right upon entry to the cave, on the bottom of a shelf on a makeshift toaster shrine.
 * X-12 research center: The Light Switch 01 Upgrade: "Smart Lights" holotape is located on the lowermost floor of this facility, leaning against a projector. The player will require a Sonic Emitter upgrade to disable the force-fields (accomplished during the Sonic Emitter Upgrade quest). This area also contains the Y-17 master trauma harness. Several more Y-17 trauma override harness units will appear if he is killed.
 * X-13 research facility, stealth testing lab: On the entrance level, there will be several rooms with catwalks looking down on the testing area. Terminals in these rooms include upgrade data as entries titled "Suggestion," or mentioning a mod or implant:
 * The weapon mod holotape enabling the "Resla Roil" modification of the K9000 cyberdog gun can be found on a terminal in the east section.
 * The weapon mod holotape enabling the "Mentat Chow" modification for the K9000 cyberdog gun can also be found on a terminal in the east section.
 * The holotape Auto-Doc Upgrade: Implant Y-7 for the Implant Y-7 perk is on a terminal in the north section (see map).
 * Y-17 medical facility: The holotape Auto-Doc Upgrade: Implant C-13 for Implant C-13 is located in the south corner of the main room, on the ground floor, propped up against a burned-out terminal. The Auto-Doc Upgrade: Cosmetic Enhancements holotape is located on the catwalk to the second floor, in a cabinet to the right.
 * Z-9 Crotalus DNA preservation lab: The holotape Auto-Doc Upgrade: Implant Y-3 for Implant Y-3 is also located on an operating table, in the room containing Shadis.
 * Z-14 Pepsinae DNA splicing lab: The holotape for Auto-Doc Upgrade: Implant M-5 for Implant M-5 is located on an operating table in the lab containing Specimen 73.

Behind the scenes
The name of the achievement associated with the previous quest (Making Friends), along with the name of this quest (Influencing People), may be a reference to the bestselling self-help book entitled How to Win Friends and Influence People.

Bugs

 * The mission arrow might still be present and indicate an area even if the holotape in that area has been collected. To prevent this from happening only pick it up when the quest tells you to pick up the specific upgrade or upgrades.
 * There may be no mission arrow if you've previously collected all mission items. This can be solved simply by exiting the Sink after completing All My Friends Have Off Switches.