Whats involved in doing a full flash from a differnt year pcm. For example, if I had a pcm from a 99 and wanted to flash it for a 2000, or if I had a 2004 pcm and wanted to flash it for a 2003? Will it matter what stock OS was in the car to start with? I have a 04 pcm and a stock 03 tune but differnt OS than it came with, if I do a full flash of the 03 tune I have with the differnt OS than the car came with will it work?