The top speed limiter is one area where the Germans can be less than precise in my experience.
When I lived in Germany I had an E46 M3. I attempted to find the limiter many times and was never successful, despite the fact that I saw 290+ kph indicated (yes, the speedo was a little optimistic, but not that much).
While the listed limiter speed is generally 250 kph, your mileage may vary, as they say. Especially on older Audi RS and BMW M models. Today manufactures occasionally offer a raised speed limiter as an option, where previously they just did it on some of the faster cars and didn't tell anyone (nudge nudge, wink wink). German engineers get a little competitive sometimes...
1M, GT4, 1969 Porsche 911 w/ 997 GT3 Cup Motor (435hp & 2,100 lbs)