The only difference between v4.0.3 and v4.0.4 is support for new Japan CN maps. Quoted from the Garmin MapInstall download page:

Changes made from version 4.0.3 to 4.0.4:
◦ Added support for new Japan City Navigator maps
So if you're not using any new Japan CN maps, just keep using the patched version 4.0.3.