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Originally Posted by 313green
and for extra credit, here's a fun sound coming from the MFI. still haven't figured it out. no air leaks, maybe a fuel leak? too lean? 911t motor sound - YouTube
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The injection pump and injectors were always noisy when warm, even in the 70's. I would suggest using some Marvel Mystery Oil in your fuel. 4oz per ten gallons is the recommended dose. You may want 6oz for a few tanks.
Modern gasoline has ethanol. Those FI pumps were designed with leaded fuel in mind. The lead acted as a lubricant. Lead is not in road fuel anymore. MMO will help lube the pump/injectors and should quite them down too.
It helps CIS injected engines too by lubing the seals in the fuel distributor and injectors. I believe it helps reduce the valve guide wear in most 911s.