Flashing an ECU

I am looking for a source, class, book, program and compiler to flash various ECU's for Fords, GM's, KIA's. Need to flash the ECU to accommodate a lean reading. So I have to be able manipulate PROM files to reset timing, A/F mixtures, fuel rail pressures, MAF values, crank position, trottle body position, etc. Any knowlegble responses would be appreciated. The vehicles I am working on are 1996 and later with OBll computer. Thanks