citroen imobiliser . ad on type?

i've got a 2000 reg semi electric pump, with the citroen immobiliser on the fuel system as standard, i have my own button to kill the starter motor, have recently fitted and alarm/immobiliser. The alarm works fine, can anyone suggest an extra circuit i can break into and immobilise? was thinking air mass meter wire, but the engine will still start with this disconnected on this model. Yes this is probably a bit excessive but if I've got the immobiliser why not use it. Any suggestions?