i made my own earthing system.
I regrounded all the stock wires and added some ground points.
I have noticed a pretty significant difference in the "performance" of my engine.....It idles better, a lil increase in gas milage (like 1 -2 mpg), and it goes through the rpms much more smoothly then before.
but my car is 8 years and 100k miles old and the stock grounds were just shit....

I replaced the stock tranny ground w/ a 4 gage wire
replaced the wire from the neg bat terminal to the chasis w/ a 4 gage
replaced the valve cover ground w/ a 8 gage
added 8 gage ground wires from the neg bat terminal to the throttle body and intake mani
and added a 4 gage ground wire from the neg bat terminal to the alternator