All A8 D3 Air Pump will fail during its lifetime ~100k+ miles. Wabco is the original company for this pump. Someone found out that Mercedes pump is being sold cheaper than the Audi Pump for some reasons. Someone also swap the Mercedes pump to run Audi Allroad which may also work for Audi A8 D3.
If the pump is being noisy, may help and they do sell the kit on Ebay.