[s-cars] Re: Most Drivability Problems Solved, and yet...

[EB]

Guys,
 
I had a problem with my S6 where it would stall when stopped (at the traffic light, for example) due to suddenly falling rpms. Restarts w/o problems, but does not respond to throttle, blows blackish smoke from the tailpipe, rpms drop and it stalls again. After a few tries things are just as suddenly back to normal - for a day or so. One other symptom was loss of power and some rpms dip while driving, although this always seems to cure by itself after 10 seconds or so. 
 
Well...I unplugged the connector to the MAFS, plugged it back, and now all seems OK!!!
 
Except - at the traffic light it occasionally (twice in 4 days so far) the rpms will start fluctuating up and down within about 2-300 rpm range, and then, after driving, it is back to a steady state. The check engine light did light a few times. Have not pulled the codes yet.  The O2 sensor is new.

Any ideas on what's going on?

Thanks a lot,

Edward