Here is a chassis dynamometer graph of the truck as we received it. This is tested on our Dynojet 248 chassis dynamometer. The abrupt end of the data is due to the factory speed governor.
This is on gasoline (roughly 9% alcohol content according to the on-board alcohol sensor).
307 hp at 5200 RPM and 332 lb-ft at 4200 RPM at the rear wheels. OEM rating on gasoline is 355 hp at 5600 RPM and 383 lb-ft at 4100 RPM. Power is right where it should be, especially when you take into account that this is with the 6L80 automatic transmission.