because the battery is at the back for the 33 u have to strengthen the ground so u run an extra 2 thick wires from the battery to the chassie. then u go thru the process of grounding components in ur engine bay that would be helped with a better ground like say the alternator, turbo, exhaust, engine block, pretty much electrical and electronic stuff. so all the DIY kit involves is a number of amp wires (coloured if u want the rice) with o-ring ends running throughout the whole engine bay and bolted to the chassie at certain points.
i came across this really cool jap site where the guy has detailed number of DIY's for his white r33 gtr and in it was an earthing section. dont know where the links gone but if u do a search in yahoo jap for earthing r33 and use babelfish its quite easy to follow.