Hope the same avatar does not confuse you, so just look at the user name.
I also do not know Drew, but just have bought his cooler kit (Transfer of funds complete Drew )
The internal gate does not restrict power , whoever told you that has very little understanding of turbos. A small internal gate will only produce uncontrolled boost creep, because it can not expel gases fast enough thus the turbine spins faster, resulting in increased boost.
235rwkw on a std hi-flow, bolted to a std rb25 is about the limits of this turbo. With the bigger ext. housing, and all the supportive parts 280rwkw (my personal experience) would probably be the max of this turbo. Sometimes a turbo will max out at 16psi, sure an extra 2psi will get you an extra 5kw, but the gain per psi is reduced, thus not worth stressing the engine for 5kw. This is caused when the turbo's efficiency range has been passed, so the turbo creates too much heat, thus reducing the power gains.