Forty-fourth Metal Gear Solid V mission is one of the repetitive ones. Its objectives are the same as in mission 13 and you can find them in its walkthrough. The most important change is that Big Boss must not be detected, because you will automatically fail. Two main difficulties are that you must not use the Reflex Mode and the Chicken Hat.
Preparing for the mission
Completing this mission in the night is highly recommended. It is helpful especially while traversing the oil field, where you can be detected easily during the day. I recommend selecting D-Dog as a buddy, since he can mark the enemies and help Big Boss eliminate them without raising the alarm.
When it comes to equipment, choosing a rocket launcher is a good idea, because you won't have to take a risk reaching the tank that is one of the main objectives.
Tips on completing the mission
The most important objectives of Pitch Dark remain the same. Below, however, you will find tips about its modifications that affect the overall difficulty.
Reconnaissance plays an important role in Pitch Dark. You should perform it after you reach the town (if you want to achieve the optional objectives) and when you reach the oil field. Try to localize and mark all of the enemies. During the infiltration, you should rely on D-Dog and use him to attack enemies without taking a risk (the mission will not result in a failure if D-Dog gets detected and shot).
Use D-Dog, your skills and weapons to make your way towards the room where the pump can be turned off. Don't forget that Big Boss needs a moment to open the door to the building and that he can escape through a window after the work is done.
Approaching the red tank with C4 to blow it up is not exactly a good idea, because you'd have to eliminate 2-3 more enemies and you could get detected. There is a much easier option - leave the oil field, go south and use the rocket launcher to destroy the tank. Remember to stand where the enemies won't notice the rocket being fired. When you achieve both objectives, quickly go south not to encounter Walker Gears heading towards the oil field (unless you wish to start the optional objective right now).