Oil being too thick, I used Liqui Moly 10W-40 grade oil which made the turbo seal go bad (it was an abused GT28 off of Shoba, so maybe the seal was bad already) and it started to leave clouds of smoke, had to switch to 20W-50 non-synthetic oil which somewhat resolved the smoke problem.
Basically it's a TD04h with CT12b housings both compressor and turbine side and was running it without any filters (open).
Can weak piston rings be a reason for oil pump seal leakage?
Thank you for the head studs suggestion; they're pretty expensive though $400 a set - Any cheaper solution to that? 
I will start the tearing down process towards the end of this week and will need a lot of help from you! 
Thanks.