There's tons of controversy out there about whether or not this mod really makes a difference. I've seen dyno tests proving it does, and I've seen dyno test showing it did nothing.
The "READ ME" link at the beginning of this post is to the full article that dyno test came from in your link. It was done by CarAudio and Electronics on a 1996 Volvo. They were seriously impressed. But, it's definitely going to vary from car to car. All I can say is those ground wires will NOT come off of my 08' Focus.
Just a quick note. I can't testify to their HP increase claims, damn don't have a dyno in my garage yet! But, I can tell you that their MPG increase claims are right on the money.
I was running 26 MPG prior to the install and I'm now running at 29 MPG (purely in-town, zero hi-way/freeway miles).