[secmil]

I know which wires are which, but I'm not sure which of them I'm supposed to be tapping into, so this question shouldn't be so model specific (1998 A4 2.8qm)...

I've read that I should be tapping into the wire that reads 0v when the engine is off, and I've seen some other suggestions for other arrangements that don't seem to apply here, so I'm sorry if this is a stupid question.

Looking at the ECU/ECM wiring schematics in my bentley manual, there are many levels of wiring that I could tap into:

-"Level 1" Would mean tapping into one of the 6 apparent leads between the ECU and the ECM.
-"Level 2" Would mean tapping into one of the six leads from the ECM to the injectors themselves.
-"Level 3" (What I hope is it) Would mean tapping into the lead connecting all 6 injectors, the wiring harness (over fuse 229, apparently), and the ECU.

Which level should I tap into? With engine off, I can find 0v on leads at each level...

Also, I realize that finding the lead that measures 0v is my objective, but at the moment I don't know which lead measuring 0v to use.