Thats an amazing DIY.
I seriously hope you are working as an electrical engineer. If not, you need to change your career!
I haven't looked at an electrical circuit since my college physics class. This is the type of stuff that confirmed that engineering was not for me. Considering the complexity of this modification, I almost feel like I got off easy by paying for the alarm installation.
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2008 BMW 535i Space Gray, Black Leather, Dark Bamboo Trim| Sport Automatic with Paddles | Sport Package
2008 BMW M5 (gone, but not forgotten) Space Gray, Silverstone Merino Leather, Madeira Walnut Wood Trim | 7speed SMG | All options
Mods: Corsa Exhaust | RPI Ram Air Intake | H&R Sport Springs | Rogue Engineering 12mm spacers