So, my brother just bought a 2013 RAM 1500 4x4 with a MDS Hemi in it...only 2000 miles on the odo (was a "shop truck" for the dealer. He claims it makes a pinging/rattling noise under light throttle or light loaded acceleration. WOT, no noise. He's tried up to 91 octane fuel, thinking it was pre-detonation, and no change. Anyone experience such a thing with the MDS Hemi? From what I understand about MDS, it cuts fuel to 4 cylinders to increase gas mileage at cruise. Could it be MDS leaning the motor out when it's not supposed to be doing so?

He has a full warranty on the truck and has taken it to two dealers. Neither claim anything is wrong. As a matter of fact, both dealers basically shooed him away like they didn't want to be bothered with it. He's at his wits end and would appreciate any feedback anyone has. He claims the noise is loud enough for other people to hear outside of the truck, so it's not a "heard inside the cabin only" type of noise. Help please!