i thought engine "crank" horsepower was independent of the exhaust? the exhaust and drivetrain are what made it lose power, so that's why you go by "wheel" power on the dyno ? if you wiki LS engines, it only mentions the engine itself when it says how much power it makes.
in any case, i thought the crank power was different on corvette because some internals were different than GXP's - but i may be mistaken.
'08 PBM GT
Roto-Fab CAI, SLP Headers, GXP Catback, Tuned
Pedders Street I, FE3 Struts
Tints, Sharkfin antenna, passenger seat mod