Increased Water Pressure after Expansion Tank Replacement
The banging in the pipes may be water hammer.

You can test your water pressure with a simple gauge. Some are sold with a garden hose fitting for easy connection to an outdoor hose bibb or to a clothes washer supply valve. Consider choosing a gauge that has two needles: one needle shows the pressure in real time while the other needle shows the maximum pressure. That second needle tells the story when there's a water hammer or thermal expansion problem. In the USA residential water pressure is often regulated to no more than 60-70 psi. Many water pressure regulators are adjustable by turning a screw on the regulator.

Although expansion tanks exist primarily to absorb thermal expansion from a tank-style water heater, they can also help mitigate water hammer. Did you confirm the air pressure in the expansion tank was correct at the time of installation? It may have been shipped with some pressure in it, but the air pressure should be adjusted to match the setting of your water pressure regulator. If the air pressure isn't correct the expansion tank can't perform its job as well.

Also, the air can leak over time, so the tank pressure should be checked occasionally.