I still think it might be the turbo seals, I have a Soarer I work on with a similar issue, nothing I do can stop the turbo seals leaking, but it isn't all the time, and mainly on decel.
Any chance you can drop the front pipe and check the dump for oil buildup? Shame the turbo is so hard to get to...
Drop two catch cans in if you can, it will at least tell you if there is an issue with the PCV or breather and rule them out.