What is the function of the sensor on the #1 spark plug wire on a 87-91 325i? I ask this question because I just realized that I raced the entire 2001 season without one. It wasn't there when I purchased the car, so I didn't know it was supposed to be there until I bought new spark plug wires and the new set had one. My guess is that it has to do with timing advance.
I'm real curious if I will see a performance change with one.