After driving my friends Camaro with one on it, I came away with the idea that it’s not even intended to be used at WOT.
It’s like the design requires there to be a high amount of vacuum in the plenum(as in throttle blades mostly closed) for it to function “properly”.

In his car, the overall driving experience was poor. There was nothing about how the motor ran that stood out at all....... other than how weak it felt when you stepped on the gas.
One would have expected fantastic throttle response with those tiny runners....... but it was not the case with that 396.
It definitely made the top 10 list of worst overall combos I’ve driven.

I would say a more realistic powerband for one of those is idle to around 2500, with light throttle openings.

Also, obviously since the runners are so tiny, the bigger the motor you put under it, the lower to usable operating range will be.
Probably not totally awful on a 273........to very unsatisfying on a 360.