If you are connected to the Internet it will phone home to Sony. Yes, Mfw builder is the only way I know of to stop it from contacting Sony If you want to keep it connected to the net. Run it on your Kmeaw PUP file but just use the privacy patches. As long as it completes without errors it should be safe to install. Keep in mind if you block playstation.net you will need to use alternate means for updating games such as one of the many game updater apps.
As far as I know, my ps3 has never had an undetected error.