I’ve owned several SAABs 99s 900s 900SPG in a high crime city. SAABs after the 99s had tank mounted electric fuel pump, accessible threw the trunk . I would cut the positive power wire on the fuel pump, run two wires up under the carpet to front or back seat, and mount a single pole toggle switch that was very easy to reach unnoticed . Flipping the switch would kill power to the fuel pump. When parking the car, I would simply switch the fuel pump off. If someone broke in and could defeated the (between the seats ignition witch) which was quite difficult those cars and start the car, said car would only run for about 15 to 30 seconds then die (with the switch off. ) I got good at being able to flip the on or off unnoticed as I pulled the emergency break. The good thing about a hidden kill switch is, during (God forbid) a car jacking, the kill switch can be turned ‘off’ unnoticed. Done as you exit and surrender the car, the car continues to run for 15+ seconds while the ‘car jacker’ gets in, drives half a block and the car dies, won’t start, the ‘jacker’ bails, you simply get in the car, flip the kill switch back on, drive your undamaged car away. I’ve yet to install a kill switch in our X3 but we no longer live in a high crime area, but im still still considering it. Not sure how difficult it would be in the X3 to run the wires under the carpet, and make the switch reachable yet hidden, i’v actually drilled the appropriate sized hole in the carpet and mounted the switch right threw the carpet under the seat, next to the parking break. Thank goodness we never needed it but it’s a cheap easy mod that can be done on any car with an electric fuel pump. An inexpensive way that Can keep your car from bring stolen or jacked. Just don’t make the switch position obvious or well known. Kinda fool proof, and it might have worked that Dodge too!!