2012 on a cold start struggles at low rpmfor approximately 10 to 15 seconds why?

My goodness, why replace all these parts at great expense and effort without testing? Testing would not have condemned the pumps because you didn't fix anything. Stop with the fuel delivery guesses. Consider that engine performance needs: Fuel delivery Ignition Spark Air to the intake (or no air) Exhaust flow Emissions controls Engine timing Engine compression Not sure why you're laser focused on fuel. Testing is needed. I'd guess emissions control or air intake concern. But check it!