Looks more like the HPFP needs some tweaks.
I read somewhere it has been looked at but not sure where that was and what is being or can be done.
I also read about the idea of a higher pressure in tank pump to feed the HPFP, I wonder if that is viable.
It seems it would be easier than messing with the HPFP and possibly safer but if there is somebody out there that knows what they are doing in the DI world that can help us that would be great!