[turboboy]

As Luxobarge says there is an "O" ring which can cause leaks, but also at the other end of the pipe is a gasket which you should change at the same time.

You have to take the pipe off anyway to change the "O" ring so it is sensible to do both. I believe the gasket is on the upper end of the oil return pipe where it is attached to the turbo under a bolted flange, held by two screws with internal splines but cannot remember the size.

I bought both the "O" ring and gasket intending to do the job myself but in the end got a local garage to do the job.