The fact that the units are grossly overcharged/undercharged tells me the previous techs had no idea what they were doing. With the modulating compressors and fans, the old rules go out the window. In the course they specify that the system leak pressurization test must hold for 24 hours. Download all the "myLink" data from the Mitsubishi website. Use the system builder tool and set up the compoonents with the actual lengths of piping. Be accurate and the program will calculate the exact charge. Spend some time reading and understanding the documentation before you start the process. Check pressurization test requirements, and follow the instructions with method. This equipment is high tech and a different mindset is required to service. I changed a compressor on a Mr Slim my own company put in. The compressor was grounded in less than a year, and I know beyond a doubt (almost) that the system was not evacuated properly. The old method (get the vacuum pump started before lunch, then charge after lunch) doesn't work. I sarted pulling the vacuum and left it overnight to get it right. It has to be done with best practices. Good luck.