If you are installing the EM on a different host, then the MOM Introscope Enterprise Manager properties file has to be updated. Also add the new server IP address to the postgres pg_hba.conf file.
If you are copying an EM directory and then moving it to a different host, then you will need to do a few things in addition to the MOM properties file and adding the new server IP address to the postgres pg_hba.conf file.
There is a file <em home>/config/internal/server/tess.internal.properties that needs to be deleted before you start the EM. If you have started the copied EM, then, you need to shutdown all of the enterprise managers (EMs), delete the tess.internal.properties files on all EMs then delete all rows in the ts_entity table.
In the copy, also you might want to delete the data directories (data and traces), remove all the logs and for good measure, delete all of the caches
Delete the <em_home>/work/Jetty* directories
Delete the <em_home>/product/EnterpriseManager/configurations (only the org.* directories and the .settings leaving the config.ini file)
If you are moving an EM directory to a new host, it is sort of the same as the copy but you don't delete the data directories and in the MOM property file and postgres pg_hba.conf you replace the original IP address with the new address.
And to be just over and safe, create a new enterprise manager directory in your source control system for the new host, and store all of the end-user modified files. I would also suggest source controlling your changes to the MOM properties files and the postgres pg_hba.conf.
Hope this helps,
Billy