To get the hidden ZBT-GEX/3000 Booster Part, choose the "Inflitrate Radar Base" mission requested by Balena. Work your way through the caverns. When you come outside where the radars are, go to the far right where there will be 6 storage units. The part is on the back side so, when your facing them, it would be the one on the left. Shoot the door and grab the part. (coordinates: X -000423, Y 000001, Z 000130)