Just to add some data points, my setup consists of this:
ID1000 injectors
Walbro 485 in-tank fuel pump
V-something Flexfuel kit hooked up to the front-most fuel line
Otherwise pretty much exactly the same setup as @
sw20kosh
I was doing some logging last night and did NOT see this issue. My E% drops about 1% point the moment I go WOT and holds steady throughout the run.