Noisy Tunzes???
Wtf. My 6055 is from the bfirst batch that came to Canada in 2008(?) and it is silent same with the two newest model 6105 I recently bought. I have had others over the years too, and have
never had a Tunze that could be classified anywhere near "loud". The only thing I can hear is if I put my ear up to the pump I can hear it ramping up in power, but they definitely don't hum or rattle. Have you inspected the propellers and housing to make sure they haven't been dropped or had sand sucked into them?