Decelerating Vibration

[DonD]

I have a 2012 V6 manual with high miles, about 183K. Runs great, other than it has a vibration when decelerating around 3K and lower RPM. If I brake really hard it seems to improve, or when I disengage the clutch it goes away. The clutch feels fine when engaging or accelerating, and shifts smoothly. Does this sound like a clutch, driveshaft, or other issue? Thanks