When does the speed limiter have to be tested?

Your answer is correct because according to German traffic regulations, the speed limiter must be tested after any change that affects the vehicle’s speed measurement or engine performance. Specifically, changes to the tyre circumference can alter the actual speed relative to the speedometer reading, and changes to the fuel supply device can affect engine performance and speed control. Therefore, testing ensures the speed limiter still functions accurately. Changes to the exhaust system, however, do not directly impact speed measurement or limiting and do not require this test. Remember this to ensure safety and compliance with German vehicle regulations.