Could be the bleed valve is knacked or blocked or something and the actuator is seeing full manifold pressure all the time ?
Try the old trusted technique of diconnecting the actuator pipe and seeing it boost up to 1.5 bar [
] Should be okay as long as he backs off at around 1 bar, try it on a motorway in 5th gear, quite easy to control boost using the throttle.
At least that will tell you if it is a tubby problem or a boost control / bleedvalve problem.
'average length member' ? Hmm..thats what my missus says...