Ya that oily residue is thanks to the vacuum created by your turbo that pulls the excess oil blowby out of your cam covers, people often use an oil catch can to stop it from building up inside their pipes. You simply re-route the pipes into the catch can, then either vent it to atmosphere or use the vacuum from the intake to help it pull the gasses into the catch can. It sounds like it doesn't do much but since there is now a large container in the path the oil stops there instead of going into the pipes.
eric