I recall when I ordered my ct200 that it was a factory thing - you specified a sunroof - no spare wheel - you specified a spare wheel - no sun roof. If you wanted to order with a sun roof and after delivery you want to get the parts and fit a spare wheel no problem. I'm reckoning that the emissions thing is the point - they've got a setup that gets under a figure with one or the other not both. The issue about passenger weight is noted but the emissions test is not done in real world ways. On flat, almost empty tank, warmed up engine, probably an underweight driver, non standard tyre pressures and all the other tricks that are allegedly used but the thing they must do is have a complete car so they don't take out the seats and if it has a sunroof and a spare wheel as standard they would both have to stay present that is unless they can show they only supply as one or the other. Crazy but there it is.