i've read hundreds of threads and ppl seem to have taken care of the prob by replacing:

motor mounts
o2 sensor
MAF
spark plugs/wires/connectors
vacuum hoses
CPS
EGR

or a combination of above. so start w/ the cheapest and move up. my car is not behaving too badly right now and i can live with it, so i'm just gonna keep on driving for a while.

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Current cars:
2001 MB E55 AMG
2003 Honda S2000
2000 Honda CRV

Gone but not forgotten:
2004 BMW 325i 5sp sport
1999 BMW 540i sport
1997 MB E420
1995 BMW M3 coupe