As SSCULLY kindly mentioned in his response, this is just the normal result of an optimized program in these trucks, and it's a well known issue due to the poor quality factory OEM serpentine belt. Many of these trucks will do that on a WOT (wide-open throttle) 1-2 upshift even in bone-stock trim. The factory belt lasts a long time before actually breaking or cracking significantly, but it's actual grip on the pulleys during a full-throttle upshift and especially it's noise characteristics are both poor even when brand new, as it's just a cheap factory belt.
When you install the Superchips tuning, not only do you get a tighter, quicker & firmer upshift at full-throttle, but you also have, for about 1.25-1.5 seconds, 40-50+ more horsepower as we've adjusted the transitional delays & retards in the program that really kill performance. The combination of the quicker firmer shift, along with the additional power, overwhelm the low-grade stock belt's ability to grip the pulleys & do it quietly.
This is easily cured with the Goodyear Gatorback (that's a specific brand *and* model of belt) serpentine belt, which we carry here at Performance. Please feel free to give us a call if you'd like to pick one up, we carry them in stock all the time. Normally I'd say you could just drop by our web site to order it, but not all our parts are displaying just yet, it'll be a week or so before they're all back up online at www.TroyerPerformance.com
Once you've got the new Gatorback belt on (and don't get anything else, only the Gatorback will do), you won't hear that sound again. It will be gone, instantly, as many people here can attest to. Installing a Gatorback belt has kinda-sorta become a standard thing to do when adding power to these trucks.
Have fun, good luck with your truck & give us a shout if you'd like help with the belt!