The usefulness of grounding kits will vary depending on who you ask. It seems to vary on the car, and the sensitivity of your butt dyno. Naysayers will claim that the act of resetting the ECU by having the battery unhooked contributes to the effect of the car running smoother. Proponents will say it improves sensor readings, among other benefits. The theory makes sense to me, I'd more lean towards seeing a benefit from doing it, but again, it depends on the car. I'm going to do it to mine eventually because I suspect I have some possibly grounding issues I've noticed in my gauges recently (most notably the EGT gauge likes to fluctuate if I have the stereo up).

My advice: If you want to do it, buy the wire from a local stereo shoppe and build one yourself. Probably $20 in parts will do the same thing as a $100 kit bought from somewhere. Heck, Franklin might be able to get you the hook up at teh Circuit City.

BTW, that "voltage regulator" is probably just a big capacitor inside a case. Same difference.