I got the dyno tune at Sams through Liverpool Exhausts.
Altogether I paid 3.2k for for tri-y headers, stainless steel cats, and twin exhaust system all the way through. Then they took it to Sam's and did the GTS maf pipe, that K&N airfilter, and mafless dyno tune.
the tune was $1000, $500 was for the GTS maf pipe, the air filter and installation (probably got a little ripped off)... and the full exhaust was $1,700
The car went amazing after that, I think they also especially tune when the Power button is on, because there is actually a significant difference in the way the car runs with the Power 'on' compared to 'off'.
I have also heard good things about Marranos Enhancement Division. The head guy there is Sonny (their number is 02 97445355), I think they are in Croydon and people on ls1.com.au reckon he is tops.
I think if you take your baby to either Sonny or Sam, you will not be dissapointed. Sonny also sells cool looking OTRCAI for genIIIs