Re: Oil in exhaust downpipe after return/feed lines
Remove turbo drain pipe at sump. Start for a short moment and see if oil is coming out, immediately turn off can once inspected.
Did you use a silicon gasket maker on the turbo oil pipe to the turbo? You are only to use a fresh metal gasket, no silicon gasket maker as often squashes in when tightening and blocks the lines.
Pull dump pipe off, clean.
Inspect turbo exhaust housing.
Oil in dump pipe usually equals turbo seal / rebuild the turbo.
Some times, alternative issue, over fueling, fuel passing through engine unburnt, cleaning old oil/muck off the exhaust manifold and collecting at lowest point / join at bottom of dump pipe.