I just bought a 06 ram hemi back in june about two weeks ago i put a flowmaster 40 series on it and had them take the res off now in low rpms it acts like it down shifts and has a drone too it.

 

Of course it has a drone, you put a Flowmaster muffler on it!!!

Everyone reports this problem who has a Flowmaster and it's exacerbated when it's on an MDS equipped 06+ Hemi.

I've got the FM 50HD and do NOT have MDS in my '04, but still have a drone at certain rpms.

Hate to tell you but you need to take that Flowmaster off and replace it. Most with MDS Hemi's opt for a Magnaflow muffler.

Oh, and your "Flow"master actually flows worse than the stock muffler you had removed...