Performance nozzles, in most cases, are nozzles that have the spray holes enlarged allowing the injector to produce a higher fuel delivery than the stock setup. The Modifications done to the nozzle will vary in both the method vendors choose to produce an increase in fuel delivery from the nozzle and the method they choose to confirm the accuracy of flow increases, and balance as a set, after the modification is made. The following lists some of the various ways horsepower gains are achieved by enlarging the spray holes of an injector: