WA at least the highest I've heard of is ~600 on a hub dyno but I dont know the specifics of the setup (a/r, boost etc). I'd say I could get there easily with more boost but who knows when the set-up will run out of legs, 'only' 25psi at the moment.
Brockas set-up is as much as 110hp down on mine under 4500, something is amiss there.