My truck has a rattle and vibration any ideas?

I have a 99 Ram 1500 and I noticed when I take my foot off the gas there is a rattle sound when I slow down that sounds like an exhaust pipe bouncing or something similar. It sounds like its coming from about the center or front half of the truck. It's not the cat converter heat shield or any pipe its all brand new. Also when I go over 45 MPH there is a little vibration in the whole truck. the drive shafts still have their balance weights and the wheels are balanced. Could these problems be connected? Everything under the truck feels solid the only lose parts are a sway bar joint and track bar.