or wire it to a variable vacum switch, so when you change gear it comes on automatically at say -10 on the std silvia gauge, the gauge max is -7, and mine idles at 6, so on over run (i.e change gear) it activates and then deactivates when back on tickover. i dontknow if its possible, but i cant see any reason why not tbh.
/me looks towards martin for this, as he always seems to be quite clued up on the stuff.
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