After reading this thread and a few others that I searched for about grounding kits I decided to make my own yesterday. My kit basically consisted of 15 feet of 4 gauge wire and twelve 6 gauge ring terminals (blue). I ground the following items:

Intake manifold to firewall
Throttle cable bolt to firewall
Throttle body to strut bolt
Firewall to negative battery post.
Alternator to passenger side strut bolt
Engine block to firewall
Used old intake manifold strap and connected it from ECU to driver side bolt

The way I grounded most of the wires was in a series so that they terminated at the negative battery post. I felt the transmission and negative terminal had a pretty beefy cable already so I didn't replace those. I am still going to do the starter today, I just ran out of ring terminals. I also used some of the old grounding wires that were there and just added some more of my own. The install looks very clean.

Overall impression is that my car lost the hesitation it was having when I would get on the gas. The idle was much smoother and didn't fluctuate the way it would before the grounding wires. The car also seems to pull smoother to redline than before. I have yet to see if my mpg went up since I just filled up yesterday, but I figure this mod won't hurt. I spent a total of $15-20 and feel this was a great investment. If anyone is interested I can post some pics up here.

99'Black GS OZ Edition