He stated in his post that he has already had his turbo checked out and it is fine. It is almost certainly one of two things. A misrouted oil return line or a mismatch between the size of the oil feed line vs. the size of the oil return line.
Have you talked to the turbo manufacturer to get specs on the size of the feed and return lines? If there is a mismatch (the feed is too big and/or the return is too small) the oil will back up and will be pushed through the seals. I am running a Turbonetics turbo and they said that input has to be no bigger than X and the return has to be no smaller than X. I don't have the exact numbers but you get the idea.
Have you verified that the return line is as close to vertical as humanly possible? Remember this is a gravity feed only so give it a clear run.