Well for MM you don't NEED to change the Chip ID as it has no online. As for MH4 I would try another chipID...you can use the GW Rom patcher to view all the chipIDs(not unique) and see which ones work for you or leave it as default and see what happens.
Very true on the MM. I'll change the chip ID back later and see if it works. If not I'll change the header back as well to see if it works
