its not that simple. you need to get an idea of how much horsepower youre going to be making. the stock ones are 210cc-but theyre not good for much more power than stock. if you go onto the Marren Fuel Injection - We Service All Your Fuel Injection Needs website they have a calculator that tells you what size injectors you need based off of how much power youre making. if you want larger injectors get a new set of name brand injectors off of ebay. i found 420? or so cc injectors, new, for $360. (they were RC). something to keep in mind is that we have high impedance injectors from the factory so you need to buy high impedence injectors or youre going to need resistors.