Recently I have noticed that when shifting in my 83' Turbo (non intercooled) a plume of smoke (bluish) would come from the exhaust (noticed in rear view mirror). Normal driving, and driving under boost does not cause this, jsut when I start the car (sometimes) and when the engine goes into deep vacuum from shifting. If get the car up to speed and downshift and let it coast down (maxinum vacuum) it does not make any smoke.

I think this is the turbo (it's maybe 60-80k old, non watercooled) but it currently makes good power and full boost. When i had the exhaust (catalatic converter) off last (a few months ago) theere was no end play on the turbine wheel, and it seemed tight. I doubt it is the valve seals beacuse the extended vacuum doesn't cause the problem.

This does not happen on every shift, but quite often. I changed to 10w 30 synthetic oil a month ago (for winter), and since then it has been worse. I used 20w 50 synthetic oil in the summer, and didn't notice this problem.

Any ideas or suggestions would be appreciated. Turbo makes normal whine noise, no screeching. Oil consumption is there, but I do have other slow leaks, and decent amount of miles (193k.)

PCV system was recently cleaned, and car passes the oil filler cap test (stays sucked down).

Thanks for any info,

Zack

PS: Could it be an intermmetent rich fuel problem. I was having problems with a super rich mixture not too long ago which was very noticable as far as smoke goes. This problem happened all the time (that the car was in boost) though.