gain in power by removing catalytic converter

[codered]

Has anyone tried yet to remove both catalytic converters and replace them with straight metal pipes?
I want to know if the e53 4.4i will still work WITHOUT the catalytic converters and with straight metal pipes instead. I heard there is an increase between 20-30HP only by removing them.
Others say that removing the catalytic converters will cause engine problems and the car will not run at all without them? Is this true or false? The lambda sensors will still be mounted, of course, but inside the metal pipes..

PS I know already about engine emissions problems due to catalytic converters removal, but there are less severe regulations in my country...

Please advise, thank you!