I think the L99 is a L98+1. The engine in the Escalade modified to fit in a lower hood is my guess. Also the L98 was the TPI engine in the C4 Corvette, with 250 hp. I highly doubt the same engine in that vette is in the Escalade. Sorry if I seem sarcastic, I do not mean to be.
Also I don't see why AFM can't be used with a manual? To me I its like saying you can't get cruise control on a manual. I don't see how its any different shutting off 4 cyl's with auto or manual if you are cruising at a constant speed. If they are supposed to turn back on instantaneously, it should not matter what transmission you have. If the auto gets significantly more MPG's, I'll have to change my mind from my die-hard manual ways, though I don't have anything against autos I just prefer shifting myself.
I may be complaining about nothing, but i'll wait for Monday for some real answers.