The power is restricted due to the air box, it's not big enough to hold all the air the engine needs. She will rev beyond 8500rpm but that's where she runs out of air.
My options are to cut the firewall and make a bigger airbox if I want to keep the MAF, or convert to speed density, remove the airbox, put some horns on the throttle bodies and let them suck air! My dyno tuner said that would give me another 35hp easy.
Your catterham guys probably don't have the throttle bodies in a box.
Nevertheless I'm quite happy with the power and it does it's job at the track very well. Autocross is more than just power, you need suspension, brakes, traction and the most important thing a driver!
Idling in grid it kinda sounds like a helicopter. Intimidating to say the least.