The most critical function of tuning software is calculating the checksum. If the checksum is calculated incorrectly (a common issue in poorly cracked software), the ECU will reject the file or fail to start the car. Official versions have rigorous testing for this; random downloads from forums do not.
PCMFlash is a specialized software integrated with various hardware interfaces (like J2534) used for reading and writing data to engine and automatic transmission control units (ECUs and TCUs). It is highly regarded by tuners for its stability and extensive module support. The PCMFlash 1.20 "Hot" Controversy pcmflash 120 download hot