Yea as above. I went to a scrappy and found a vacuum control solenoid from a fiesta. To fit connect the vacuum solenoid valve with a good t-piece in the brake vacuum line. (make sure the T-piece is secure as when you really need those brakes you may find theyl not be very usefull if the vacuum line has disconnected or is leaking!) Run a vacuum line from the vacuum solenoid valve to the dumpvalve.
The microswitch will need to be placed where it will be triggered when throttle is released. Youl prob need to make a bracket. Use a inline fuse obviously and you have the option of putting a switch in there to stop it working when you dont want it. This allows the dump valve to get the vacuum signal needed to open the dumpvalve. Its pretty pointless on a diesel but i do love the noise
