I have an '05 Ram 4x4 HEMI QCSB, also had couple of 5.2 Magnums, and the Magnums can't hold a candle to a 5.7, not even close. Maybe you're still used to how the Cummins drives. A friend has a '10 (basically same truck as yours) with an aftermarket ram air, MRBP exhaust an a Diablo tuner and the thing goes like a scalded cat. Mine has a set of Chinese shorties and a better exhaust and it goes pretty good. Shouldn't a '15 have an 8 spd? Is it a dial or a shift handle? An 8 spd is going to be shifty as they're programmed to keep the engine in its happy place. They also take awhile to figure out how you drive (adaptive learning)