My ES-P with a TSIO 550E, 660 hrs since new, no longer reliably idles unless the electric fuel pump is running on low.  This is new behavior in the past 10 hours or so.  The engine is stock except for GAMIs and was originally set up to SID 97-3E but the fuel system hasn't been touched since then.  It's apparent from the G900X's fuel pressure display that the idle fuel pressure is too low, and we can most likely readjust the pressures back to spec.  But my question is  "is the low idle pressure simply normal wear and tear, or is something abnormal happening?"

I plotted the minimum idle fuel pressure for the last 450 engine operating hours (MinimumIdleFuelPressure.jpg).  Each marker is the minimum fuel pressure during a single flight while the engine was idling at start of the flight.  I defined idle as engine running for at least 45 seconds, RPM between 700 and 1000 RPM, and oil temperature 120 degrees or cooler.  It's clear to me the minimum idle pressure has been slowly declining for the entire time, but it started a steeper drop about 100 hours ago.

I plotted the minimum fuel pressure during climb, when the boost pump was likely off (MinimumClimbFuelPressure.jpg).  Each marker is the minimum fuel pressure during a single flight.  I considered data points where the RPM was between 2450 and 2550, MAP between 29 and 32, and altitude below 9000' -- I think these are likely times when I had not activated the boost pump.  I don't see anything weird about this plot, other than the minimum pressure has been rising (?)

Neither my mechanic nor I really know the wear pattern for the mechanical fuel pump and related assemblies.  I really want to conclude that we can simply adjust the fuel pressure back to spec and keep flying.  But there is so much expertise on this forum, I'm wondering if anybody has better advice.

Thanks
isaac heizer
N7842K