Looking for thoughts from the collective minds of the LML.  Last flight in my IO-550 normally aspirated legacy, I noticed surging in the engine with the low boost pump on. I did not notice any surging when I turned the boost pump off. Also did not notice any fluctuation in RPM. Nor did I see any fluctuation in RPM when I downloaded the engine data. The obvious question would be what are the possible causes and does it make the airplane unsafe for flight as there is no surge when the boost pump is off. I don't understand how I could feel and hear surging in the engine yet see no fluctuation in RPM, so I'm stumped. Any ideas would be appreciated, thank you. Art

Sent from my iPhone; Art Jensen