Here is a youtube video I shot just now.
https://www.youtube.com/watch?v=2RDVdoktvCU
Sorry got the phone a little too close on the right side but you should be able to distinguish the kind of chuffy sound the right is making vs the left.
It's a 3.0L with a dual exhaust so outside of the cat, or some sort of ignition issue, what could cause this?
Should also mention that when in drive, stopped at a stop sign or whatever, the idle is consistent but kind of grumbly sounding. Can feel some vibration. Would a cat getting blocked up cause the idle to sound and feel this way?
Bernie