Crikey. I don't even remember having an account on Audiworld, let alone that thread. I do remember T8 locking its wheels at random - the pedal worked fine on that though. I did briefly wonder about the ABS pump for this, but the pedal behaviour has nothing to do with that.
I think it has to be a mechanical failure in the servo tbh, or something in the pedal cluster. Removing the vacuum removes its power assistance, but the master cylinder is still pressed closed by the servo. If the master cylinder was jammed closed the servo would simply return to normal position - it pushes on the master cylinder piston, but there's no fixed connection between them.
There are some pretty hefty coil springs inside the servo - one of those may have snapped and jammed it shut. Yes, its the black thing attached to the pedal box.
Its the same between RHD and LHD btw. Prestige appear to have a few in stock
