2018 Chevrolet Tahoe Suspension Problems

4100 Miles - Asked service dept. at dealership to check for noise coming from underside of vehicle. No service was completed. 4800 Miles - Asked service dept. at dealership to check again for noise on suspension. Service indicated it was a parking brake cable that was rubbing. 9800 Miles - Asked service dept. at dealership to check fluttering noise coming from engine. No service was completed. 15,000 Miles - Asked service dept. at dealership to check again for rattling noise coming from engine. Service indicated fluttering heard was exhaust pulsing through the manifold. No service was completed. 21,000 Miles- Service Dept at dealership provided multi point inspection and given clear inspection. No service was completed even though I stated there was still engine noises. 24,000- Asked service dept. at dealership to check hard shifting from transmission and poor performance. In addition, mentioned the noises again. No service was completed, service stated it was due to colder temperatures. 25,000- Asked service dept. at dealership to check hard shifting from transmission and poor performance. In addition, mentioned the noises again. Engine cooler lines were replaced. Scanned and verified clutch learn values all normal. Activated TCC and disabled TCC and found normal operation. No service completed. Now, after warranty has expired, service at dealership is telling me my camshaft and lifters need to be replaced, struts are leaking, transmission needs attention and should be flushed, and that I should NOT be driving my vehicle due to safety concerns. Although, I had taken the vehicle in multiple times during warranty period with complaints about these very items, no service was ever completed to correct them. Since then, I have read multiple articles documenting GM issues with L87 6.2L engines and transmissions. I'm filing a formal complaint with GM, as these issues should have been communicated to consumers or fixed through recalls.