pull the intake pipe off the turbo and check for play on the wheel...side to side and in and out. Also, pull the up pipe and check for oil in the pipe....better yet, pull the intercooler loose from the compressor housing of the turbo. Oil there at the outlet of turbo is a sign. If you still have the breather connection from the valve cover to the inlet, it could pull oil through as well. That bypass is cheap. But if it's smoking heavy, I bet bad turbo seals as a first try...compression test/leak down test as a second. PCV issues as a third?