Engine: B5254: clouds of blue smoke after the overun on acceleration

[100K+]

Hi guys Trying to get to the bottom of this issue as above. The only time I notice smoke is after a length of time with the engine on overun at say 35/40mph then when I accelerate, plumes of blue smoke can be seen in the rear view mirror.
My thoughts are
1) Valve stem oil seals... classic culprit for these symptoms - but in recent years you don't read that much about their failure...and I have no smoke on start up when the oil would have had chance to seep past the seals overnight. All I have is just steam as you'd expect.
2) PCV system clogged.... I have started to strip down the engine, but I'm stuck at the LHS lower inlet manifold bolt - its covered by another part which needs another part removed to gain access. So I'm having 5 minutes think and have decided to seek advice/comments on my situation. As an aside the glove test on the oil filler cap is a loss.... It gets SUCKED down into the filler - good job theres a mesh screen or it would disappear.
3) Some type of turbo/seal failure....There is a little oil on the surface flange of the over the engine top intercooler pipe, but no signs of oil having been in the pipe - but would there be??
I'm wanting to get this repaired but would prefer to choose the right culprit -
Cars a 2004 V70 AWD R 120K miles. As ever all comments/suggestions welcome. ( Wife said i should plug the computer in - as it cost all that money -trouble is I don't know what questions to ask it.)
Cheers
Bob.