OK, so I took the car to the dealer for diagnosis - here is what they said:
"Checked for surging when idling and found codes for air flow meter and oxygen sensors. Checked Oxygen sensors - tested OK. Checked computer and check for vaccum leaks and found throttle body actuator leaking also found air flow meter may be faulty but could also be symptom of air leak.
Recommend replacing throttle body first."
Now the bad news:
Throttle Body part: $1536.00 + labour $515.20 = $2054
Air Flow Meter part: 427.00, labour $184.00 = 611
What would be the impact if I delay fixing this for some time? Dealer told me horror stories - engine would be getting unfiltered air, and may wipe enough oil off cylinder walls to cause damage...