so YNOTP you recommend i put a muffler on to avoid any problems? with the stacks?

hi i have a 2001 ram 2500 cummins and i want to run straight pipe stacks is that legal these trucks never had cats on it yet and its a diesel and i want to run twin 5" stacks please let me know or do i have to have at least a muffler on it cause apperently the turbo acts as a muffler too