A method for correcting injection behavior of a fuel injector designed for injecting accurately metered quantities of gaseous fuel and liquid fuel respectively comprising: (a) in a fuel injector family calibration phase performed at least once for a family of fuel injectors: operating a set of fuel injectors from said family of fuel injectors at a first predetermined number of engine operating conditions, the operating conditions comprising a gaseous fuel rail pressure (GFRP), a liquid fuel rail pressure (LFRP) and a cylinder pressure (P CYL); and determining a multi-variable function of said engine operating conditions based on measurements of performance of said set of fuel injectors; said multi-variable function determining a nominal value (x OD, x CD, x FTM) of a fuel injector family characteristic; (b) in a fuel injector calibration phase performed during manufacturing: operating a fuel injector from said family of fuel injectors at a second predetermined number of engine operating conditions; and determining a function of said nominal value (x OD, x CD, xFTM) based on measurements of performance of said fuel injector, said function of said nominal value (x OD, x CD, x FTM) determining a corrected value (OD, CD, FTM) of said fuel injector family characteristic for said fuel injector; (c) in a fuel injector trimming phase during operation in an internal combustion engine: operating said fuel injector at an engine operating condition; calculating said nominal value (x OD, x CD, x FTM) of said fuel injector family characteristic from said multi-variable function; calculating said corrected value (OD, CD, FTM) of said fuel injector family characteristic from said function of said nominal value (x OD, x CD, x FTM); and employing said corrected value (OD, CD, FTM) when actuating said fuel injector to inject fuel. (a) in a fuel injector family calibration phase performed at least once for a family of fuel injectors: operating a set of fuel injectors from said family of fuel injectors at a first predetermined number of engine operating conditions, the operating conditions comprising a gaseous fuel rail pressure (GFRP), a liquid fuel rail pressure (LFRP) and a cylinder pressure (P CYL); and determining a multi-variable function of said engine operating conditions based on measurements of performance of said set of fuel injectors; said multi-variable function determining a nominal value (x OD, x CD, x FTM) of a fuel injector family characteristic; operating a set of fuel injectors from said family of fuel injectors at a first predetermined number of engine operating conditions, the operating conditions comprising a gaseous fuel rail pressure (GFRP), a liquid fuel rail pressure (LFRP) and a cylinder pressure (P CYL); and determining a multi-variable function of said engine operating conditions based on measurements of performance of said set of fuel injectors; said multi-variable function determining a nominal value (x OD, x CD, x FTM) of a fuel injector family characteristic; (b) in a fuel injector calibration phase performed during manufacturing: operating a fuel injector from said family of fuel injectors at a second predetermined number of engine operating conditions; and determining a function of said nominal value (x OD, x CD, xFTM) based on measurements of performance of said fuel injector, said function of said nominal value (x OD, x CD, x FTM) determining a corrected value (OD, CD, FTM) of said fuel injector family characteristic for said fuel injector; operating a fuel injector from said family of fuel injectors at a second predetermined number of engine operating conditions; and determining a function of said nominal value (x OD, x CD, xFTM) based on measurements of performance of said fuel injector, said function of said nominal value (x OD, x CD, x FTM) determining a corrected value (OD, CD, FTM) of said fuel injector family characteristic for said fuel injector; (c) in a fuel injector trimming phase during operation in an internal combustion engine: operating said fuel injector at an engine operating condition; calculating said nominal value (x OD, x CD, x FTM) of said fuel injector family characteristic from said multi-variable function; calculating said corrected value (OD, CD, FTM) of said fuel injector family characteristic from said function of said nominal value (x OD, x CD, x FTM); and employing said corrected value (OD, CD, FTM) when actuating said fuel injector to inject fuel. operating said fuel injector at an engine operating condition; calculating said nominal value (x OD, x CD, x FTM) of said fuel injector family characteristic from said multi-variable function; calculating said corrected value (OD, CD, FTM) of said fuel injector family characteristic from said function of said nominal value (x OD, x CD, x FTM); and employing said corrected value (OD, CD, FTM) when actuating said fuel injector to inject fuel.