Had some mechanic tell me the stock fuel rails were good for up to 400 Horsepower. Obviously you would need a good fuel pump 155 litre per hour or bigger and a fresh fuel filter hehe .
Hink
i made over 400rwhp on the stock rails and the car was running rich so it could have supported more. ive heard the stock rails will go to 500 but dont know first hand
Due to the physical routing and sizing of the injectors' supply lines, the last injectors in the line (the two rear cylinders on the left, numbers 7 and 8) will be the first to see a reduction in delivery pressure and/or volume under high-demand operation. This is not normally encountered in an OE-type straight EFI application, but may occur when increased delivery demands are placed on the system.
The production fuel delivery manifold tubing has an inside diameter measuring .192 inch. Although this is more than adequate for the flow volumes required by most normally aspirated applications, the line's relatively small diameter amplifies pressure pulsations within the tubing caused by normal injector and pressure regulator cycling. Larger tubing increases the delivery system's capacity and reduces the pulses' pressure and frequency.