It has been gone over time after time. You should do a search, ACCORDDUST. I am not trying to be an ass by saying "search nOOb!" but I am just saying that there were some really good disccussions about how well these "earthing" systems work.

But to sum it up in a few lines:

-If you can crimp, buy your own wires and connectors. It'll save you a few bucks.

-If you have a stock stereo system or if the car is not drawing more current than OEM specs, and your wiring is in decent condition...save your money and time and skip the upgrade.

-I am going to say that it DOESNT "improve" performance. I mean if your current grounds are rusty and corroded, and the connections are loose and weak; you are probably losing some power. So replacing the wiring will "improve" your performance since performance was lost due to the shooty electrical system.

-If you run a big stereo system you will want to upgrade the main wires with something thicker. Chassis to battery, alternator to battery, engine to chassis.....