I think your missing my point, don't badge a car as a 2.0 litre if it isn't, or an AMG if it isn't AGREED.
But badging a car as a 1.8 when its an M3 is equally as stupid IMO. The only reason to do that is so that you can feel like a big man when someone who doesn't know what the car is isn't expecting you to beat them when you have a traffic light dash, but IMO that you makes you a complete tool. A car is what it is, leave it like that and don't be so stupid.