What exactly does replacing the fuel rail from stock, to lets say, an AEM high pressure fule rail? Does anyone know if any compnay makes one for a 2005 civic lx auto?

 

More fuel available for injectors. Totally unnecessary unless you have larger injectors, a turbo, N2O or a SC. AEM would be the company I would look into, not sure if they make them for non-EX vehicles though. Might be able to use an EX fuel rail.

 

What about Fuel Pressure Regulators? What is their purpose and availability for my car?

 

FPR are same thing, more fuel to the injectors, do a google search something will come up.