The lid and exhaust can be bought a lot of places.... Thunder Racing has their stuff together and good customer service. http://www.thunderracing.com/

I have Ls1Edit, which is old school but works...HP Tuners is where it is at as others have said. It's not a hand held, you use your laptop...You are just paying for the cable really. The good thing about HP is it is two in one meaning you can scan the car during WOT passes (I have to use Auto Tap then switch to Edit) and change anything in the pcm with one cable...it's also faster/safer uploads than Edit. Lastly, if you ever go boosted, they are the hottness when it comes to 2-3 Bar tuning....right now i am outflowing the mass air meter and having to add fuel in manually...meaning on cool days the car runs lean, on hot days it runs pig rich...which of course varies power output by quite a bit and i have no room for error with my boost levels.