IMO it makes sense to beef up the car's OEM electrical connection for the sake of knowing u have a damn good ground everywhere in the engine?
The production grounds are plenty (you think maybe the factory engineers might have thought of this, too...??). Just another geegaw to separate you from your money. If you doubt the grounds are sufficient "invest" a dollar in a foot of 00 welding cable and two crimp on connectors and bolt it in yourself. You wouldn't get the free stickies but it would work just as well.... You are not going to get more HP and torque from a ground strap....sorry. Now those magnets that you stick on your fuel line to align the fuel molecules are known to work..... LOL LOL LOL
If the ground strap between the engine and body was too small this might help BUT it really doesn't address the issue of the individual circuits.Each circuit has it's own ground. This kit doesn't address that. I think it's BS.
I looked into this myself a while back. And to my suprise the N* already has beefy grounds to all the points a 'earth ground kit' or whatever will want u to hook up to.... I undestand a lot of the import crowd uses these kits because their OEM grounds simply dont cut it...
I've said this before in other forums. It applys here also.
In Hot Rodding there are two rules;
1) You are trying to undo what it took a whole team of engineers to do.
2) You can never over ground an automotive electrical system.
If you want to buy a "Grounding Kit", what ever that is, then it won't hurt a thing. The only thing to never ground is anything that carries the power. Seems obvious, but you never know.................................