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Dell: That dark bulb is the IAT - Intake Air Temperature sensor. Definitely clean it, but more importantly, clean the MAF - Mass Air Flow sensor wires 'concealed' up inside the black plastic MAF tube.
IIRC, a dirty MAF sensor will under-report the quantity of air, so the EMC will inject less fuel than the engine really requires, causing a lean condition, particularly a rough idle when cold.
I can't count how many friend's engines instantly ran smoother after we spent ~10 minutes spraying ~50 cents of MAF cleaner on the factory original sensor with 100+K miles accumulated road grime.