Compression test will tell you if it's the rings. Also, when you pull the spark plugs, look into the cylinders and check for oil pooling on the top (or coolant/water).
What turbo are you using? Cheaper turbo's will have cheap thrust washers that will cause a leak once they are overburdened.
Valve stem seals will not create a cloud of smoke that you are experiencing so you can scratch that off.
Last time I had a friend have this symptom it ended up being an incorrectly gapped and clocked oil control piston ring.
Bookmarks