what revs do they run and how quick does the system need to respond to give no fuel?

are we talking absolute ideals here or not?

you are trying to get the most out of your set up and pushing the limits of boost/detonation temps etc....

is it SAFER to fuel on overrun in terms of running lean etc?

or is it down to the driver aswell....

say you are doing top speed attempt - you reach your limit for distance... you brake and back all the way off the throttle what happens?