Just as a data point, I had rich condition stuff, mostly on hot restart. I replaced the accelerator pump in my YF based on feedback I got here. It cured the condition. There was no visible tear in the old diaphragm, nor did it “feel” notably rough. I also checked the pump “bonnet” as per Jon G’s procedure while doing this jump. It was not warped.
All I can figure is that the old pump had a pinhole that I couldn’t see.
