The pump doesn't put out pressure. It only sees flow. The pressure comes from the oil being restricted to flow through the block and parts. The higher the pressure, the more stress on the pump, and more power is lost trying to turn the pump against the higher pressure. A lot of people think higher pressure means better lubrication but that's not how it works. The pressure only insures the oil reaches the parts. It takes less than 10 psi at 1000 rpm to keep supply up throughout the engine. Most people aim for 20 psi at idle to extra safe. Power loss starts to occur at around 25 psi. Above 60 psi, the strain on the oil pump drive really starts to add up. At this pressure, the oil starts to heat up a lot from compression. The rule of 10 psi per 1000 rpm still rings true. The bypass for the oil pump should ideally open around 60-65 psi, which you shouldn't be getting close to until 5,000+ rpm. Once the oil reaches the bearing, rings, cams, etc... dynamic viscosity and pressure is no longer relevant as kinematic viscosity takes over. When the oil is dragged and spread through the bearing by the crankshaft's rotation, the oil doesn't see the pressure from the pump. It's now only affected by centrifugal forces and gravity. The pounding from combustion against the rod bearings determines shear action. Too much lubrication from too high of viscosity, while not as dangerous as too low of viscosity, can still cause excessive wear and localized overheating in the rotating assembly.
In the vast majority (95+%) of street engines, a high volume pump is not needed. The only time you really need a high volume pump is if you have wide bearing clearances with a lower viscosity oil with high a high flow rate through the bearings. The high pump is needed in those cases to keep up with demand. We're talking .0035" or greater clearances though.
I don't like the idea of a restrictor on the turbo feed. To me, that's just band-aiding the real problem of too high of oil pressure to begin with. The turbo doesn't need pressure, this is true, it needs flow. When you put in a restrictor to keep down pressure, you also decrease the flow. You're making a compromise that shouldn't have to be made.
1993 Camaro bracket car
2002 Tahoe family/tow rig
2006 Altima daily