Maybe they are super conductors.

As an EE I have to agree with most of the comments. Grounding is not going to increase HP. But if you are running a few thousand watts of subs you will need better wiring all around, including more batteries and/or capacitors.

All car companies have some of the best EE's in the world. I worked for Ford a long time ago, at the time any improvement that was possible, was made. Do you think that if a couple dollars worth of copper would give them 5 HP they would ignore it?