stock pump with non modified oil galleys.
Just reasons/examples...
High volume with modified= When someone go's through the galleys/passages opening'em up/cross drilling/taping lines across the lifter galley, they're usually racing and have race app clearances .0025+ or what ever, beside the fact that if they messed with all orface sizes dictate pressure too.
How about cam priority oiling?
Then there's bearing clearance app [again], might need the high pressure/volume with real loose clearances=You know.. the guy with tired motor that has decent cylinder pressure so he decides to do a gasket reseal and pump change, or better yet the guy that does the re-ring/bearing deal but the mains/rods are loooose
the more you compress oil/fluids the more heat you make and the more hp you eat up.