Turbo Oil Feed Torque Tip
The line delivering oil to the turbo's bearing has an O-ring around the pipe within the banjo fitting. If the banjo turns while applying torque to the bolt, the pipe can become cocked at an angle squeezing one side of the O-ring and opening a gap on the other. I believe when this happens oil is allowed an exit path, and this is the main cause of leaks at this fitting. To keep the banjo in line with the pipe, wedge something on its side to prevent it from turning while tightening.