I have a 2007 1500 QC 4X2 Laramie 5.7 Hemi. I dropped a Flowmaster exhaust in it when I first got it. It sounded great the first few weeks, now it sounds like a dying calf when I'm driving under 50mph with Overdrive on and MDS on. I have noticed that I when I turn OD off the MDS doesnt turn on and the truck sounds great with horrible gas milage. I know when the Flowmaster was installed the rear resonator was taken off. I have also noticed a loss of power over time. I need to do something quick. Any recommendations?