I reckon you are close there Mitchy.
The culprit is the fuel flow limit, which makes them run at much lower rpms than we are used to hearing.
I would suggest ditching the flow limit, retaining the total fuel use limit, and raising the rev limit. They still wouldn't sound like a v8, still quieter, but pretty horny.
Blow off valves etc have no place with these regulations, as excess pressure is harnessed as electrical power. That's one of the components of that lovely whine you can hear as they come into corners off throttle.