To check if your combi boiler provides a sufficient flow rate, you can perform the following test:
1. Turn on all of the hot water taps in your house.
2. Measure the flow rate of the water from one of the taps using a measuring jug.
3. If the flow rate is less than 9 l/min, then your combi boiler may not be compatible with the Mira Event XS power shower.
In this case, you may need to consider installing a booster pump to increase the flow rate of water to the power shower. A booster pump is a device that increases the pressure of the water coming into your home, which can help to improve the performance of power showers and other water-consuming appliances.