Did you read close enough to see that the guy who made the post said EXACTLY the same thing I told you? That the grounds are for the guages, not the motor. Any time you hook up an electric guage, you need to give the guage a decent ground. Since the engine really has no (nor needs any) reference ground for any of the sensors (besides the O2), if you connect an air/fuel guage to the existing O2 sensor, you need to use the O2 sensor ground (pin 49), so it has the proper reference. As I said before...adding 1, 10 or 50 extra ground straps won't make any difference in how the car runs, the ECU doesn't ground to the engine in any way. It can affect the guages, since in many cases they do ground through the engine, but a guage doesn't need a battery cable for a ground, since they barely carry any current at all. If your sender has one wire on it, it grounds through the engine, if it has two, it does not.