Our B's throttle body is run by wire and is prohibited to manual force opened the flap. From my own experience, i force opened throttle body flap to clean it with a cloth. At first nothing abnormal happened after cleaning and my B's engine become very smooth and powerful!!! however, after few days check engine light suddenly triggered. I learned from others that this symptom of check engine light ON is very common for run by wire throttle body. I searched from other forum and found a method from someone to start engine ON and OFF for more than 10 times to clear the engine light but have no luck. Very next day miracle happened, the check engine light gone. I don't know if it will come back again.
I started looking for method to calibrate the throttle body and many info from other forum.
These few days i will try to put at ignition 2 to stay for 30sec before start the engine to have throttle body do calibration before engine running.
And yes, the engine light never come back again.