When does the speed limiter have to be tested?

You answered correctly. The speed limiter must be tested after any change to the effective circumference of tyre size or the fuel supply device. Changes to the tyre circumference can affect the accuracy of the speed measurement, and modifications to the fuel supply can alter engine performance, both of which could impact the effectiveness of the speed limiter. Changes to the exhaust system, however, do not directly affect the speed limiter’s function, so testing is not required after those modifications. Always remember that proper calibration of the speed limiter is crucial for safety and compliance with regulations.