The canister under the car on the drivers side (US) is the fuel filter. The main fuel pump is mounted in the fuel tank, accessible by removing the back seat, and then removing the cover plate underneath the seat cushion. From under the car it would not surprise me if you could hear the pump running. You should usually be able to hear it kick on from inside when you turn the key (before starting).
Sorry, but I've no experience with the injector noise issue.