Tuning on these modern cars can be tricky, You can get a simple hand held tuner or a full bolwn software and interface depending on deep and how much time you want to spend learning, or you could take it to a pro. You can pick either kind up used on another forum if you wait for a deal. There is a guy around here that is very reputable in all of the LS circles, ED Hutchenson (I may have butchered his name). He may be able to do it by mail. The forum to check is
http://www.ls1gto.com/forums/
There are also a lot of backyard tuners who can probably do a good job, but that is hard to know. I had a diablo hand held and have moved up to HP tuners Pro, but I am still learning.