412 Sprinter, mystery oil leak?

[motovelo]

My 96 Sprinter has covered over 375,000 trouble free miles and apart from an incredibly noisy diff is still 100% reliable, however it has developed a mystery oil leak that apears to be coming from the pipe that runs from the rocker box to the bigger pipe that runs from the inlet manifold to the turbo. At first owing to the fact the oil had dripped all down the front left hand side of the engine it appeared as if either the rocker gasket or the sump gasket was leaking but after removing the pipe from the inlet manifold It has a pool of oil collected just inside the main inlet branch where it goes in to the five inlet manifold tracts. Am I right in thinking that maybe the turbo is knackered and is blowing the oil into the inlet tract and then out of the breather from the rocker to the turbo?? I've tried to explain this the best I can and I'm hoping somebody will have had a similar experience! The turbo seems to work fine and I hear it whistling away when driving but did notice when removing the pipe the other day that there appears to be quite a bit of fore and aft movement in the impellor/rotor?