One of my co-workers has an '05 Duramax 2500 HD crew cab - loves the truck except for one thing: under hard acceleration (full or close to full throttle) the truck hesitates. Is this the defueling I have heard about to preserve the tranny? If this is the deal, is there any way to improve it? Truck is not modified.

It almost feels like the wastegate has opened at the wrong time. Only seems to do it in first gear. It is significant, and it bothers him. If it is "normal" at least he will have something to work with.

Thanks,
KC