... I don't think that there is any "lead" buildup, since leaded fuels have'nt been available for 25+ years. ....

Leaded gasoline was not banned in the United States until 1996. See these sources:

http://worstpolluted.org/projects_reports/display/66

http://en.wikipedia.org/wiki/Gasoline

http://www.epa.gov/history/topics/lead/02.htm

So a car that had been parked since 1989 (as was stated by the author of the thread) would likely have lead anti-knock compound residuals in the exhaust system.

I stand corrected. I keep forgetting that California is not like the rest of the country, in more ways than one! Leaded fuels have been gone here for a good 25 years, at least in the bay area. I still doubt that there is a buildup of "lead" deposits, at least in amounts to cause health problems. The gunk on the air injection tubes is pretty much the same as the carbon buildup that you get on the valves, which I suppose should'nt be inhaled no matter what they are made of. Maybe if we have a chemist in the group they could shed some specific light on the subject?