Here's a suggestion for you future PO (previous owners). The FO (future owner) may appreciate your consideration.
Document whatever hi-tech vehicle kill, alarm system you have in your car as soon as possible before, during and after installation. Draw wiring diagrams, wire color codes and identify locations of alarm modules and file it away for future reference by whoever is going to inherit or service the system - it may even be you in a few years when you forgot how you did it in the first place. This goes for any DIY install that involves the factory wiring harness (headlight relays included).
If you purchased a used 911 (most of us?) you realize how difficult it is to reverse-install those modules/circuits that control ignition/starter/fuel pump/remote control/door lock/siren/windows/flashers, etc. The installation is often performed by the guy at the local car audio center who may not care how and where things are installed (hidden) as long as it "works".
my $.02
Sherwood Lee
http://members.rennlist.org/911pcars