I would bet the smoke is probably oil burn from worn VGS's. The tell tale sign is when the smoke is mostly prevelant during startup and idling. Some say it's "blue" smoke but to me it just looks like, well smoke...

My 95 has had the smoke since about 85K and now I'm right at 200..No immeadiate Ill effects, but It took two tries to pass smog last year. I think the smoke degrades the efficiency of the cat converter and also cant be too good for the O2 sensor...Probably puts alot of carbon into the EGR ports...

So in my opinion its not an urgent thing..but not something you want to let go for 100K like me <img src="/forums/images/graemlins/shiner.gif" alt="" />