I don't know about the 01's, but i know one of the reprograms i had done to mine had a "turbo-saver" feature that was kicked on. It does exactly that now, the turbo is silent until it reaches whatever the parameter is and then once it's there, i got my air whistle back.
So it's probably normal, gotta let them warm up or they are rolling doorstops. Go easy on it when it's warming up, you don't want to wash the cylinders.
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'06 Inferno Red 2500 QC, Auto, 285 70 17 BFG AT KO's, Century Ultra Topper, CoolPipe, Icebox w/4091, Amsoil's in da pumpkins and xfer case.