It's entirely possible it has a cutoff switch and I am just unaware of it. My comments also derive from experience with my own brick, which is one of the earliest 700 turbos available (1985 745t) and would be the one lacking an electrical cut-off if any of the years do.

The existence of such a cut-off might also explain why my brick "reset" about 8 years ago when my actuator hose fell off and I ovberboosted. However, I think I can safely say that the device is not on or attached to the intercooler since I've pulled mine innummerable times and never, ever seen any electrical or mechanical device attached to it. Only two hoses on the intercooler, the in and the out air hoses, with an oil drain plug at the bottom.

UPDATE: after reading the next post I think he may be right about the dash unit. When I recently replaced the vacuum hoses in my brick I found a device under the dash connected to the hose to the boost gauge via a T split. I wasn't really sure what this device's function was, but I guess it would make sense that it reads the same vacuum the boost gauge does and actually reacts to an overboost condition. It's directly above the gas pedal to the right and below the steering column.

That hose acually slips off as it gets oily with time, so it might be important preventetive maintenance to give it a look from time to time and make sure its still hooked up.

-rt