Generation IV Internal Engine - L92 differences and LS3 intake questions

I've got a L92 out of an '08 hummer that I'm going to swap into another car...

First question is what the difference is betwee the Hummer, Denali and Escalade that cause the variance of HP between the different platforms. Is it an intake/exhaust ducting issue, change in cam or change in tune that causes the roughly 25 hp range between the different vehicles?
2008 Escalade 403hp/417lbft
2008 Hummer 393hp/415lbft
2008 Yukon Denali 380hp/417lbft

2nd question is what is the deal with the complete LS3 intake manifold with injectors, fuel rail, TB, etc? I found a part number out of the GMPP catalog but no one sells it. I know the L76 manifold assembly was discontinued but what about the LS3 version that was supposed to replace it?

I don't know about the differences but I bought a complete LS3 intake with rails and injectors in really good condition off of ebay for $430.

I asked the exact same question in my own thread a while ago. Everyone basically said they are the same, they just want the "Escalade" to make the most power because its a flagship vehicle, like the Corvette wont ever be out powered by a Camaro.

I bought the L76 intake, throttle body, fuel rails, injectors, MAP sensor, etc for $530 from Scoggin way back when also. I thought it was too good to be true, and apparently it was if you cant find it anymore!

Edit: I found the thread for you too look at if you want...

http://www.ls1tech.com/forums/generation-iv-external-engine/925208-380hp-denali-l92-vs-403hp-escalade-l92.html