Scott--as we tell everyone that has an issue like you are describing, check the actual fuel pressure with a know good mechanical gauge tee'd into the FP hose. That way you can see if its a 'real' pressure fluxation, or instrumentation.
But from the sound ot things, with no other erratic engine operation, no surges, no rpm or map, cht, egt fluxuations, it points to a sender/wireing/ground/power, interface problem.
Tom Swearengen, TS Flightlines LLC, AS Flightlines
Joint Venture with Aircraft Specialty
Teflon Hose Assemblies for Experimentals
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RV7A Tail Kit Completed, Fuse started-Pay as I go Plan, on hold while we develop new products for RV builders