Sorry but I'm going to have to strongly disagree here. With a $35 wiring upgrade (reduces duty cycles by a real 10-15%) and a BAP the stock fuel pump is plenty strong for 500hp. At 425 you have tons of capacity to spare.
On the other hand if you plan on forging the engine and bumping it up a notch then the GT500 fuel pumps are great. I put them in my Bullitt when I went from 505hp to 600+.
Agreed. What size blower pulley is on there..and how much boost? If it's just the oem edelbrock 5 psi, you sure don't require megabuck GT-500 pumps. You need a hand held tuner and /or something like an aeroforce gauge, so you can see all the various parameter's.... like Fuel rail pressure..and fuel pump duty cycle. Mine stumbled badly when I tried to get into boost...last summer, turns out it was a clogged fuel sock, that goes over the bottom of tyhe fuel pump. Once that was cleaned out, the fuel pump duty cycle dropped like a rock. Also the fuel rail pressure was back to it's normal 40 psi under all conditions. When was the last time the fuel filter was replaced ?
With the simple 10 ga wiring mod, the fpdc is now down to 78-80% @ wot. (6 psi boost). The boost could be increased, and the simple 10/8 gauge wire mod is still sufficient. Any more than that, then a simple BAP could be added. Whether a BAP is installed, or the GT-500 pumps, either way you still need to increase the wire gauge 1st.
With 5-7 psi boost, plugs are gapped to .035". With 8-9 psi boost, plugs are gapped to .032" If somebody has swapped plugs and used the oem gap, you will end up with misfires /stumbling etc. You can read the number of misfires right off the obd port. When I installed new plugs, correct heat range, and gapped to .035", misfires dropped to zero.
With out further info on what was done to your car, and other mods, what octane tune was used, whether it factored in E10 etc, you are flying blind. Do you have a boost gauge ? Are you using the correct fuel? Not being able to read items off the obd port, while driving.... drives me nuts. Even if GT-500 pumps were installed, they require a new tune..and they also require the wiring upgrade. The wiring upgrade is simple, just one piece of wire..and one relay.
