Well, on this one, there is one wire bundle coming out of the ECU going to the engine via the driver's side of the car, and another bundle off that same connector going to the engine via the passenger side of the car. I see no good reason why these two bundles ultimately have to plug into each other up front, unless these are ground lines and are being tied together to complete some shielding in these bundles. But if that were the case, then why not just have each end ground to some common point on the engine instead?
This will make more sense once I get that other harness out and see where things go tonight.