The Grundfos pump on my Baxi Combi 80e boiler continued to be noisy despite opening the screw on the automatic air vent when refilling the system. I loosened the large silver bleed screw on the pump while the heating was running which released trapped air and reduced the vibration. The noise was completely deadened by jamming a piece of foam behind the cold water supply pipe.
There was also "kettleing" noise from the boiler's heat exchanger just before it cut out after refilling the system, despite adding Sentinel X100 corrosion inhibitor. The noise disappeared after a month presumably after dissolved air had been removed from the water.