First off it Stazi - no extra n.
I think that the way the ECU works is that it monitors fuel pressure at the rail and will proportionally increase voltage to the pump until it is satisfied that it has the fuel pressure required. That is not to say that if you fitted something like a 260lph Supra pump that it would be able to regulate something that big. It may have a hard time keeping the pressure low enough, depending on what sort of voltage resolution the ECU has i.e 0-14V or say 10-14V
Nonetheless I can say that I have yet to see any adverse effects to using this pump.
Pump per say are not return/less, they are just an electric motor, and as such will pump according to the voltage supplied.
The Eclipse used a "return" style fuel system with manifold pressure enrichment, i.e. as boost increased the signal to the FPR would increase and thus proportional close the return orifice to increase fuel rail pressure. Voltage was held constan at ~14V, when running.
I do not have a fuel pressure regulator, but I am confident that if I were running into problems they would be almost instantly evident. My fingers are crossed that it won't throw a "fuel overpressure code", but I doubt it as I am not running rich anywhere. My fuel maps stayed the same.
