To add on to the original thread, if you always want the latest official version, get it from pinball.com - they're not going to post any of the post-factory revisions people cook up, although you might think they're quasi-official because when you get them from other sources (like ipdb) they have the williams license boilerplate attached. It would likely be a lot of work to figure out from the code end what was changed which is why I always encourage the rom modders to use some of the empty space in a rom (there's usually some!) to put a changelog within the rom itself that anyone could read with a hex editor.