I've learned that some entrained oil in the intake system from the turbo is to be expected. If it is beginning to come out and drip on the ground I would inspect for leaks. I would first determine if is really coming out of the intake components. Check the turbo resonator (2004 - 2006), hoses, charge air cooler. If it's coming from a hose it could be a loose clamp or the hose beginning to split.
It would also be possible for the oil to be coming from elsewhere and getting blown onto other components to make it look like they are the source.
I believe the pre 2004 models are known for a bit of oil coming out of the EGR system.
https://sprinter-source.com/forums/showpost.php?p=55450&postcount=7
I know your Sprinter is 2006, but I think it still applies. (Thanks for including that on your signature. I wish everyone would do that.) My 2004 has a bit of oil that seems to get around underneath, but so far I have not noticed any drips. I do wipe things off a bit if I'm under the van for other things so that may be why I don't see any dripping. Sorry I can't be more definitive. AP/vic
Edit: This is somewhat unrelated, but it reminded me. I find it interesting to note often there's a dirty spot on the highway where there is a bump. I figure it is from all the little oil drips on vehicles that are just hanging on until they are jostled loose by the bump. Maybe my oil drips are knocked off because our roads are so terrible.
Simple things just amuse me I guess.