I believe you have found the problem.
My 91 350 blows oil through the intake. Im sure the turbo Seal is bad.
That would account for the oil loss. I use about a quart every 3000 mi.
I also have oil weeping past the intake gasket oiling the drivers side of the engine. Not much but enough to know there is a problem. Break out the old shop vac. I rebuilt the turbo on my 1980 Mustang years ago.
Im sure its not to difficult.
-Anthony