Yes u can use safc on a 4g15 engine.. as long as it is not a step 2 engine i.e car model 2000 and above are fitted with siemens ecu which cannot be fitted with safc.. but before u do decide to fit in one.. go for engine mod first.. such as cam.. tb.. overbore the intake and so on.. that will give u a nicer response when u tune the car with safc.. but do bare in mind.. a stock ecu will need at least 2 to 3 days time to relearn all value from the sensors before it can perform at its peak.. do a lot of research first before u do anything... u'll save a lot of time and money.. ;)