Well I am not really sure what you have done to your car in the way of mods. Simply in any case with more fuel you need more air so that you can make a bigger bang. You need to keep the air and fuel mixture realitively stoich for the most pure power.
So in any case if you getting more air into the engine then you want to run more fuel. Depending on how much air is flowing into the engine you should be able to figure out how much fuel you are going to need to make a nice stoich reading at WOT. Just get a S-AFC and you can use that to set your Air/Fuel Ratio and it has volt indicator you can use as a guage to set it correctly.
Finally if you want more HP NA, then get NA cams to draw in more air. There a million other things you can do to draw in more air, of course a new filter will work quite well, as well as ram air. Anything that makes it easier for the engine to draw more air in will allow you to add more fuel. As for running a high flow fuel pump, you can easily do it with a good aftermarket FPR. That is what I am doing on a Turbo setup and it works well.
You can set the duty cycle higher but that is not recommended. Since then the injectors are basicly stuck open.
Inj. Size(lbs/hr) X Duty Cycle / BSFC = HP per injector.
280cc / 10.5 = 26.6 lbs/hr
26.6(lbs/hr) X .95(95%dutycycle) / .50 (b.s.f.c) = 50.54(hp per injector)
50.54X 4(number of inj) = 202.16hp
But there are other key factors that can change the output, these things are Fuel Pressure and BSFC (Better the fuel the lower the number)
One good cheap mod to do is the Parallel Fuel Line Conversion that way all your injectors get a more equal amount of fuel, where as stock they do not.