As far as the big boom noise that everyone seems to have honed in on lately, I think it's the brake booster and some type of pressure slamming into it at start up. Not sure why it only happens intermittently. As for the high speed valve train clatter that is definitely the lifters. Being a die hard Ram fanatic, I hate to say it but it is embarrassing to buy a brand new truck and have that kind of noise at start up. And for you guys that say, no big deal it's under warranty, some day it won't be and some day you will want to sell the truck. If a buyer comes to look at your truck and you start it up and boom, tick tick tick tick...no one is going to buy the "oh, it's just a Hemi thing, haha.