Check out the horsepower goals in the aftermarket section at the top should give you some ideas. If more questions just ask everyone here is good about answering with there experience.
Basically say 175/80's are 175cc's of fuel and the second number is a percentage over the stock nozzle size on he injector. In this case 80% over a stock nozzle. There shouldn't be too much more til you get into 7.3l coded injectors