It sounds like the rear seal in the turbo is gone , An easy way to confirm this is to start the motor and block off the crank ventalation outlets in the cam cover as to build up a bit of preasure in the crankcase , inturn this will also create preasure in the turbo center housing and if the seal is gone this will force oil past the seal into the exhaust housing causing your exhaust to blow smoke . ( do this test at operating temp )