What's the best wire for a theft deterrent (I bypassed vats)? If I have a switch that opens a wire to the optispark (crank sensor?) will that keep the injectors from firing at all? Or should I use a wire that powers the fuel pump relay?

 

If you open wiring that inputs to the pcm (like opti), you will get a code. Maybe better to do the FP relay. Shouldn't be any problems with that.