What fuel are you running? Do you have a Alky kit? Theoretically the 255 pump should flow enough for 500hp on gas but you would probably be out of injector before then.
Get a set of 60-80 pound injectors. Like mentioned, 255 is good to 500 hp. Not sure on a 5.7 car but on my 6.1 chip I have a wot afr of 10.4:1 which is a bit rich. Over 800mv on the NB.
42lb injectors and a single nozzle and an I tank pump should do 25+psi on your combo.
You need to see fuel pressure and methanol pressure in real time to verify the fuel system is working properly.
If the chip was burned with 25psi and your at 750mv now something is off.
Eric is not off on his fueling usually.
You can add and should wot fueling in the chip but if the pump or alky system isn't working properly then it cant add
Take a pic of the chip and post it here. You could also just look at what paperwork was sent with it but there could always be a mixup so a pic of the chip is most accurate way for folks to help.