Some time ago, my i6 petrol engine has erratic idle at start almost at every refueling. Sometimes the engine light comes on and the message ‘reduced engine performance’ appears on the message centre. Other times I get only the erratic idle. If I turn the engine off and on again everything goes back to normal.
The strange thing is that happens always at the petrol station after refueling. I tried different stations and brands to make sure that is not fuel quality related.
Is someone else faced the same problem? Is it due to MAF, or some other sensor or something else?

Try to run the engine with the fuel tank cap open.
If the eratic idle appears, then could be because of a defective EVAP canister purge valve.

Thanks for the answer, I will give a try with a cap. Otherwise there will be a trip to the dealers.

I tried to run the engine without the cap. No problems at all. So may be something else.

I had a trip at the local dealer today since the erratic idle was coming from time to time. The diagnosis was misfire at 4,5 and 6 cylinder due to clogged fuel injectors.
I had the injectors cleaned φορ 50€, so hopefully that was it.