I had a DSport mag where they looked at all the grounding kits they tested over the years. It was hit or miss on which cars gains and which didn't. Don't think it even favoured the older cars. Very random. I'll see if I can find the magazine...
Edit: OK, this example isn't great because these are probably modded cars, and it is a mix of turbo and NA, but here it is:
That Sun Grounding kit is 3 gauge, and the Apexi is 8 gauge. Neither are cheap.