Helllo,
My Porsche is 1972 911S with a stock mfi.
I have a problem of that the idle speed slows down to 800rpm after coasting downhill for some time or shifting down to the lower gear before stopping the traffic signal.
I have checked the RPM transducer and the micro switch work correctly, which make the shut off solenoid on the pump also works correctly. If I leave off the pedal at more than 1500rpm, I can hear “click” and the engine speed comes down to 1000rpm immediately. The idle speed except those cases is 1000rpm in steady.

What do you think that my problem with mfi comes from? Any suggestions or comments are welcome.

Thank you
Takahiro