I have a three year old Weil-McLain Ultra hot water boiler/instant hot water furnace. It has rumbled ever since the installation. I've had the company represetative here as well as the installer and no one can fix the problem. I have multiple zones and each time a zone demands heat, the boiler rumbles loudly enough to shake the floors. :( I have tried restricting the air silencer, but in doing that the furnace pops like a firecracker! Our gas pressure has been checked by the gas company and it is normal. Can anyone give me some advice as to how to fix this problem?? Thanks!