Blue smoke is oil, which rules out any fuel injector leakages or fuel pressure regulators. If the engine has a lot of miles on it, it could be the valve guides being worn.
Bur, I would first suspect the cheaper alternative needs to be looked at. And that is the oil breather system. After the engine is warmed up, take out the oil dipstick and with a piece of paper, check the suction at the opening. If there is none or air is coming out of the pipe, you have a clogged line between the oil separator and the intake at the turbo.
Replacing the oil breather system with new parts takes several hours for a good mechanic and about $150 in parts. This will eliminate the pressure inside the crankcase and save your engine seals from developing leaks.
If the problem is the valve guides, then the valve cover must come off. Not an easy DIY project.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)