i know this has been done to death but hear me out, there was confusion with doing it & i think i have figured a way to do it easily.
Micro-switch on fuel pump (throttle lever)
wired to solenoid which is attached to a vacuum pump & this will give the vacuum for the dump valve
it seems very simple
if anyone can see why this cant work then please post below
otherwise i will have a nice sneeze on me nova!