My '04 is rated at 295hp. Overall, I'm impressed with the 5.3. It's a great compromise of performance and economy. I've read some articles on those who have swapped out the 5.3 for the 6.0 - (in an Avalanche), and the performance gains were negligible. I believe you may have twin electric radiator fans, where I have engine driven.
The 'throttle by wire' is nice. If you've never had this, there are some driving, er, throttle behaviors to know. For instance, when just cruising on the Interstate, and you want 'passing gear', a slow, steady, depressing of the accelerator to the floor, it won't do much. But, if you rapidly floor it, it will kick down to low 2, and go. It seems to sense the
rate of throttle movement, and act accordingly. I believe torque management plays a roll here. At WFO, mine shifts at 5250rpm. I've had mine up to 95mph and it was still pulling. I'm not sure what the MPH 'de-fueling' threshold is.
FYI, the bed of my AV is not 100% water tight. In a heavy rain, it'll leek a bit at the seals between panels. I believe this design hasn't changed with the new body style.
A power back window would be nice.
