Passat (B5) :: Vibration Mostly Off-throttle At Highway Speeds?

for the last several weeks, I've noticed a problem that seems to be getting progressively worse... there is a vibration seemingly from the front end (possibly passenger side), and it only appears on the interstate at typical highway speeds (70-75 MPH). facts:

1. It does not happen below ~70 mph.

2. It doesn't appear to be a wheel bearing - no noticeable change in tone or "amplitude" while turning at speed.

3. I use cruise control all the time on the highway, and it is more noticeable going downhill (increases in vibration), when the engine is obviously off-throttle.

4. The car is a 99 V6 5mt.

5. The axles that are presently on the car are Raxles, and have been on it for ~4 1/2 to 5 years.

6. I recently changed over (this past weekend) to my winter/stock wheels and tires, but it was doing it with the summer wheels and tires.

7. It happens regardless if the gears are engaged or not (5th or neutral - I coasted down a hill on the interstate today in neutral to add more info).

8. I've replaced the wheel bearing on the passenger side about 6 weeks ago.

I'm thinking I have an inner CV Joint that is starting to fail. The boots are intact, as I inspected them recently while replacing the clutch/pressure plate/throwout bearing/flywheel. The transmission axle flanges had no play. The vibration was occuring prior to when I changed out the clutch.

Thoughts? Inner CV joint, or...???