If you imagine a huge fuel pump. It pumps a huge volume of fuel. That fuel travels along a fuel line, some of it is used by the fuel injectors, and then it comes to the fuel pressure regulator. The only problem is that the fittings and internal galleries on this fuel pressure regulator are much smaller than the fuel line and fuel rail, and so the regulator cannot regulate the fuel pressure down to where it needs to be.

We all know that increasing fuel pressure means you get more fuel per squirt right?
Well that may be true, to a point.