My apologies, i thought you mentioned the rocker breather pipe, for that you can disconnect from the airbox.
If your air box to turbo pipe is showing signs of oil then it's likely the turbo output shaft seal has gone, a simple way to check is remove the pipe from the turbo and give the shaft inside the turbo a wiggle. If it shows signs of damage to the outside of the blades and has play in the shaft ( sideways/up/down movement ) then it will be time for a new or replacement turbo, there are folk who have stripped their turbo down and replaced parts but it's not a straight forward job as such.
If it's a 19J engine then you can pick them up fairly cheap enough ( complete engines ) with the turbos still on them.
A downside to the 19J is the heat generated by the lack of intercooler, this can ( and does! ) cause cracks within the turbo body ( i've had 2 cracked, my current one has a hairline crack ) which in turn can cause problems within the turbo housing of seals etc.