I have a friend with an '02 HO and he's always preached do not reflash because it electronically detunes the motor. Every time he's had his reflashed at the dealer he experiences a very noticable loss of power (power returns but only after working the truck hard for a period of time). Since I've been lurking here I've noticed that reflashing is commonplace. Do the 3rd gens also experience a power loss afterwards or is this a 2nd gen issue? Is this really an issue at all?

 

I did not notice ANY power loss on mine, but DTR member Deavy Huty has a 05 and he has been telling me he swears that his truck lost power after his flash this last week.

 

The PCM is adaptive. There is nothing wrong with recalibration updates.
Some drivers notice it and some don`t. But like you said, it returns to normal after a while. This is due to a complete system reset. It needs to relearn. Normal...