I replaced a few parts on my 2007 Mustang V6 (174,000 plus miles) such as the serpintine belt, belt tensioner, PVC valve, spark plugs (double iridium) and harmonic balancer. All of those replacements brought down the rough idle/vibration (on a scale of 1-10) from a 10 to a 7.

I then bought some new stock Motorcraft motor mounts and had a local shop install them. I saw the removed units and they were cracked and one was leaking. You can't tell if they are jacked because they have a rubber cover over them when mounted, so you have to take them off to see how bad they really are.

So, the rough idle/vibration was not caused by the transmission or torque converter THANK GOD!!

Thanks everyone for your help especially 08'MustangDude regarding the engine mounts!