Of course you can run without a boost controller.
I have done a fair bit to my car, I am running natural boost (used to be 12psi on the factory RB20 turbo, now 10psi with a 25DET turbo). Not 'factory' boost as a lot call it, as its higher than factory boost.
As long as your boost level is safe (not too high) and it maintains stable boost, there is no 'need' to use a boost controller!
[edit] to add to the above comment, it will run actuator boost IF there are no mods. Once you add breathing mods (POD, exhaust etc) boost will increase a bit!