So a fuel pressure regulator sits beyond the fuel injectors, so fuel pump > Fuel rail/ injectors > Fuel pressure regulator.

When a fuel pressure regulator is operating as it should, its 'leaking off' excess pressure.

For example, if a fuel pump is supplying a fuel rail at 4 bar of pressure, yet at idle the injectors only require 3 bar of pressure, the fuel pressure regulators job will be to reduce this rail pressure to the desired 3 bar, it'll do this by releasing this 1-bar/ opening enough to reduce the back-pressure on the system to 3 bar.

But when the engine is running, the fuel pressure is going to drop as the fuel injectors are opening, which means the pump has to flow more to meet the demand, subsequently the FPR will continue to try to achieve its rail pressure by reducing the flow through it (on a boosted setup it'll increase the fuel pressure it due to the additional boost pressure within the manifold 'fighting' the fuel pressure)

To drop fluid pressure requires little volume due to it being pretty much incompressible, so the fuel flow through the regulator should be relatively low as long as your fuel pump is working correctly (not running max amps when not required)

The long-story-short. It should be fine, as when the flow is higher, the engine is consuming the fuel in theory and shouldn't be passing (in large volume) through the pressure regulator. If you want complete security; a fuel pressure transducer wouldn't be a bad idea, and can be plumbed into the ECU as a additional safety margin (if fuel pressure drops cut ignition etc etc)

http://injectordynamics.com/articles...ure-explained/
this might be worth a read