Its official....the TT-RS achieves 255 with relative ease.
Is it speed limited? The Germans have a whole thing abut the 250km/h mark, but some special models leave the factory uncorked. AMG used to neuter all of them, and then sell you an ECU mod to unleash it. For about $2-3K depending on model!! Robbery!! My C36 would run into the limiter at 250 pretty hard, so I thought about the mod, then found out what the cost was for the extra 25 or so km/h. Ouch!!!
A friend of mine had a modded E55 and we saw 301 via GPS. Solid as a rock. I had the Porsche to about 270, but man, that car was HAIRY at that speed. Porsche said the body (whale tail, etc) was to help high speed stability, so I'd hate to have seen what a standard coupe would have been like at those speeds. Undriveable, methinks.
The Miata is great to 150, starts to get a little light after that, and a little scary over 180...