IMO it's best not to work the EBC too much, they need some room (duty) to help maintain boost levels.
i have an 8psi spring fitted to my setup and will comfortably hold 16psi all the way to the limiter, when i turned it up to full it hit 22psi and backed off to 17.8psi.
when i put my other spring back in to hold 15psi, it should hold 2BAR with enough spare duty to help with top end.