Does the 550 Maranello, 1998, by any chance, meet the Euro 4 Petrol Emission Standards? I believe it is only Euro 3.
It looks as though it may actually only be Euro 2: http://eurostandards.co.uk/ (works for UK registrations only - I entered mine and it came up with 2). BUT see https://www.rac.co.uk/drive/advice/emissions/euro-emissions-standards/ - very useful website and note in particular: "Be aware of websites that claim to give you accurate information on your car's Euro emission standard by entering your number plate - as of 10 November 2017, the RAC understands there is currently no comprehensive online look-up website for UK drivers." There should be a label on our cars somewhere, maybe on the door frame.
And I found this on Ferrari's website: Urban test cycle ECE (Version "Euro 2") 35,6 l/100 km Extra urban test cycle EUDC (Version "Euro 2") 15,5 l/100 km Consumption ECE+EUDC (Version "Euro 2") 22,9 l/100 km CO2 emissions combined (Version "Euro 2") 530 g/km Urban test cycle ECE (Version "Euro 3") 38,2 l/100 km Extra urban test cycle EUDC (Version "Euro 3") 16,4 l/100 km Consumption ECE+EUDC (Version "Euro 3") 24,4 l/100 km CO2 emissions combined (Version "Euro 3") 558 g/km which seems to suggest that the 550 was both to Euro 2 and Euro 3 - presumably early cars 2, later cars 3. But not 4. This is in line with the tables on the RAC website. It also seems to suggest that the cars to Euro 3 were worse polluters / less economical than cars to Euro 2, which seems to be a bit strange! I found this plate on my car: Image Unavailable, Please Login so I wonder if this means it is Euro 3 compliant? This would seem to conflict with the assumption that early cars were Euro 2, as mine is a 1998 built car.