I make them and sell them here and on ebay (username michaelgw). With a V6 you shouldn't have any troubles. VS and VT V8's (non ls1) need slight modification to the techedge circuit.
There is plenty of info on this site if you want to roll your own.
As to what you can do with one go and look at efilive.com and download V4. That is the only program that will work with these cables.
You can't do any tuning, it is for diagnosis only.
HTH
Mike