That can be tricky. First, you have to find out exactly where the oil is coming from. My guess would be in the area of oil drain off of the turbo. It could be a gasket or o-ring between the turbo and the oil drain. There could be a seal in the turbo itself leaking. Another spot is around where the oil drain goes into the valley pan. The grommet could be cracked and not sealing. Another thing could be the valley pan itself. They all have a baffle underneath them to keep the oil splash out of the CDR. The later ones will let the oil drain back into the lifter valley pretty well, but the earlier ones sometimes won't let that happen. At higher RPMs, thee oil will build up inside this baffle and then will come back out around the grommet. The solution is to put a hole (or several small holes) in the baffle right under where the oil drains into it. One time, I put a reman engine in a truck with a turbo (it seems like it was either a Factory Turbo or an ATS093). No matter what I did, oil would seep out around that grommet. I even pulled the grommet back out and put RTV around it to seal it to the valley pan and around the oil drain itself. It still leaked. I finally pulled the turbo off again and put a hole in the baffle. That stopped the leak. After that, every time I installed an engine that had a turbo on it, I always put a hole in the baffle. I put one in mine last year, even though it's N/A for now, I'm going to install a turbo soon so I planned for that. Whatever you do, don't drill a hole. This will drop meatal shavings into you engine. You can use a hammer and a center punch. Some people talk about using an ice pick to put several small holes in it. I use a punch tip on my air hammer. I put a hole in it that's around 3/8" to 1/2". That's big enough.
