1. Check if you secondary air pump is working, thats the main contributor for airflow during cold startups. Also check your thermostat as it sends out readings to your ecu telling it whether the engine is cold or at running temp and alters the engines rev. A good way to check if your thermostat is functioning would be to switch the A/C off and power up your car, If you see the fans working then u found ur problem. "Do it first thing in the morning", I had the same problem and replaced the thermostat it had been fully open by some fellow and the ecu throught that the engine was hot and kept the fans working for 15min even when the key was removed from the car.
2. This could be your ignion pack they are a common issue, are u experiencing it when u try giving it some gas... e.g overtaking
3. Well this has so many factors, this is what i did to bring it from 5kmpl to 8kmpl
Replaced ignition wire,coil and plugs
Replaced egr value
Replaced bank(2) O2 sensor
Cleaned Injectors
Throttle was electronic so couldnt do much...
Plugged the diagnostic tool and fixed everything it had reported... upto now its zero faults.... and does 8 to 9 depending on how i drive...
What i have mentioned is specific to VW
otherwise... just give Ruwan a call.. he will sort you out....