I used the below vids, watch out for chapter 7 (Hideout) and 11 (U-Boat) as hes missing one on each. To watch them on the PS4, come to this guide and watch on TT, for me if I try to watch them on their youtube page it says a plugin is needed :(
Chapter 7: Ashtray thanks to Oliver
Go down in to the sewers and keep on going until you fight those little flying robot things. If you look ahead there should be a big opening in the floor where the water goes down... If you look down there you'll see a hole just big enough to do a running jump to get in. Once you get in, walk up the stairs and it will be on top of the petrol canister.
Chapter 11: Enigma
Enigma 6:3 Is across the hall from 6:2