2002 575 fuel problem

Hi if my 575 has stood for a few days & you starts it up, it runs poor on maybe only on 6 & engine light comes on, if you then remove filler cap & retighten & disconnect/reconnect battery cut off, engine light goes out car runs pefect for the rest of the day.
Id been told to make sure the fuel cap was tight & the seal was ok, but this seems to be the opposite, letting a little into the tank seems to fix it, are there any breathers which maybe blocked or any sensor to check ?
thanks andy