Give Manny a call at Super Street Performance/R&R Auto. They are in Farmingdale 631-770-0146. Not sure if they do LS motors, but they have a chassis dyno and access to tuners in case they don't do it in house. PM me if you want more info.
I know the guys/gals over at digitalcorvettes.com rave about this one guy that does tunes for their cars, LS engines. They all say he does a great job. I do believe he's out of Pennsylvania??
Hope this helps.