issues with 2015 gmc sierra 1500, "whistles" with rise in rpms=main

[geljr]

Bought a new 15' sierra 1500, 5.3L v8 6 spd, at 3000 miles a whistle noise started occurring everytime it downshifts; hit gas, rpms jump, shift, then let's out a high pitched whistle. Dealer says they located the cause in the throttle body case but noise still occurs after replacing. They ten said the located noise in the exhaust system, replaced but no fix. Has anyone else experienced a noise like this? They're telling me it's a characteristic of the exhaust and they won't proceed with anymore repairs, but I haven't heard anything close to the noise in mine in 4 other trucks with same setup. Aside from this, I had the front left breaks fail at 24000 miles only on front driver side, water leak from under frame into cab, tailgate misaligned, and that's all so far. Truck is 6 months old, 27000 miles, clearly a lemon, but gm and dealership are playing games. I have dealership on either neglegence (careless documentation on break system and bad repairs/install), best case for them. Or outright fraud, falsifying repair/servicerecords. 5000 miles= 8mm break pad left, 12000miles= 7 mm front, 6mm back, 18000 miles= 7mm front/back, 24000 miles front left pads gone rotor severely damaged, replaced both sides on front, didn't report cause of defect or pad life for front right and didn't report on anything for the back. I don't understand why big companies get away with this type of shit. Luckily I have the documentation, recorded conversations, and all 3 ways to claim a lemon, but they aren't making it easy. I feel I should sue them for fraud, putting myself and others at risk of injury/death for putting a defective vehicle on the road with a compromised brake system. Has anyone else dealt with this type of situation?