So the 91 525im blows bluish smoke under vacuum conditions. It appears to be getting worse, requiring less 'coasting in gear' to produce the smoke and stink out the area. Last time I brought this up, I believe it was Bill R that said it may not be serious, so I kinda put it on the back burner. I must admit, its beginning to get annoying. The shop that did my cylinder head work a year ago doesn't seem too willing to investigate and believes there is no chance of valve seals being responsible as everything was fresh when the head went together 30,000km ago.
So, what method would work best to determine the source? I have a comp. tester and may be able to find compressed air or have another shop perform a leak-down test. How about PCV system, could it be a culprit? I'd just like to know the probability of it being head related so I can pursue it with the shop, or, take care of it myself if its in the bottom end (less likely I presume?).

Thanks again all.

Dave M